





Internet Engineering Task Force (IETF)                          P. Hoyer
Request for Comments: 6030                                 ActivIdentity
Category: Standards Track                                         M. Pei
ISSN: 2070-1721                                                 VeriSign
                                                              S. Machani
                                                              Diversinet
                                                            October 2010


                Portable Symmetric Key Container (PSKC)

Abstract

   This document specifies a symmetric key format for the transport and
   provisioning of symmetric keys to different types of crypto modules.
   For example, One-Time Password (OTP) shared secrets or symmetric
   cryptographic keys to strong authentication devices.  A standard key
   transport format enables enterprises to deploy best-of-breed
   solutions combining components from different vendors into the same
   infrastructure.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6030.

















Hoyer, et al.                Standards Track                    [Page 1]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................4
      1.1. Key Words ..................................................4
      1.2. Version Support ............................................4
      1.3. Namespace Identifiers ......................................5
           1.3.1. Defined Identifiers .................................5
           1.3.2. Referenced Identifiers ..............................5
   2. Terminology .....................................................6
   3. Portable Key Container Entities Overview and Relationships ......6
   4. <KeyContainer> Element: The Basics ..............................8
      4.1. <Key>: Embedding Keying Material and Key-Related
           Information ................................................8
      4.2. Key Value Encoding ........................................10
           4.2.1. AES Key Value Encoding .............................11
           4.2.2. Triple-DES Key Value Encoding ......................11
      4.3. Transmission of Supplementary Information .................12
           4.3.1. <DeviceInfo> Element: Unique Device
                  Identification .....................................13
           4.3.2. <CryptoModuleInfo> Element: CryptoModule
                  Identification .....................................15
           4.3.3. <UserId> Element: User Identification ..............15
           4.3.4. <AlgorithmParameters> Element:
                  Supplementary Information for OTP and CR Algorithms 15
      4.4. Transmission of Key Derivation Values .....................17
   5. Key Policy .....................................................19
      5.1. PIN Algorithm Definition ..................................23
   6. Key Protection Methods .........................................23
      6.1. Encryption Based on Pre-Shared Keys .......................24
           6.1.1. MAC Method .........................................26
      6.2. Encryption Based on Passphrase-Based Keys .................27
      6.3. Encryption Based on Asymmetric Keys .......................29




Hoyer, et al.                Standards Track                    [Page 2]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


      6.4. Padding of Encrypted Values for Non-Padded
           Encryption Algorithms .....................................31
   7. Digital Signature ..............................................31
   8. Bulk Provisioning ..............................................33
   9. Extensibility ..................................................35
   10. PSKC Algorithm Profile ........................................36
      10.1. HOTP .....................................................36
      10.2. PIN ......................................................37
   11. XML Schema ....................................................38
   12. IANA Considerations ...........................................44
      12.1. Content-Type Registration for 'application/pskc+xml' .....44
      12.2. XML Schema Registration ..................................45
      12.3. URN Sub-Namespace Registration ...........................46
      12.4. PSKC Algorithm Profile Registry ..........................46
      12.5. PSKC Version Registry ....................................47
      12.6. Key Usage Registry .......................................47
   13. Security Considerations .......................................48
      13.1. PSKC Confidentiality .....................................49
      13.2. PSKC Integrity ...........................................50
      13.3. PSKC Authenticity ........................................50
   14. Contributors ..................................................50
   15. Acknowledgements ..............................................50
   16. References ....................................................51
      16.1. Normative References .....................................51
      16.2. Informative References ...................................52
   Appendix A.  Use Cases ............................................54
     A.1.  Online Use Cases ..........................................54
       A.1.1.  Transport of Keys from Server to Cryptographic
               Module ................................................54
       A.1.2.  Transport of Keys from Cryptographic Module to
               Cryptographic Module ..................................54
       A.1.3.  Transport of Keys from Cryptographic Module to
               Server ................................................55
       A.1.4.  Server-to-Server Bulk Import/Export of Keys ...........55
     A.2.  Offline Use Cases .........................................55
       A.2.1.  Server-to-Server Bulk Import/Export of Keys ...........55
   Appendix B.  Requirements .........................................56














Hoyer, et al.                Standards Track                    [Page 3]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


1.  Introduction

   With the increasing use of symmetric-key-based systems, such as
   encryption of data at rest or systems used for strong authentication,
   such as those based on One-Time Password (OTP) and Challenge/Response
   (CR) mechanisms, there is a need for vendor interoperability and a
   standard format for importing and exporting (provisioning) symmetric
   keys.  For instance, traditionally, vendors of authentication servers
   and service providers have used proprietary formats for importing and
   exporting these keys into their systems, thus making it hard to use
   tokens from two different vendors.

   This document defines a standardized XML-based key container, called
   Portable Symmetric Key Container (PSKC), for transporting symmetric
   keys and key-related metadata.  The document also specifies the
   information elements that are required when the symmetric key is
   utilized for specific purposes, such as the initial counter in the
   HMAC-Based One-Time Password (HOTP) [HOTP] algorithm.  It also
   creates an IANA registry for algorithm profiles where algorithms,
   their metadata and PSKC transmission profile can be recorded for a
   centralized, standardized reference.

1.1.  Key Words

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

1.2.  Version Support

   There is a provision made in the syntax for an explicit version
   number.  Only version "1.0" is currently specified.

   The numbering scheme for PSKC versions is "<major>.<minor>".  The
   major and minor numbers MUST be treated as separate integers and each
   number MAY be incremented higher than a single digit.  Thus, "PSKC
   2.4" would be a lower version than "PSKC 2.13", which in turn would
   be lower than "PSKC 12.3".  Leading zeros (e.g., "PSKC 6.01") MUST be
   ignored by recipients and MUST NOT be sent.

   The major version number should be incremented only if the message
   format (e.g., element structure) has changed so dramatically that an
   older version implementation would not be able to interoperate with a
   newer version.  The minor version number indicates new capabilities,
   and it MUST be ignored by an entity with a smaller minor version
   number but used for informational purposes by the entity with the
   larger minor version number.




Hoyer, et al.                Standards Track                    [Page 4]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


1.3.  Namespace Identifiers

   This document uses Uniform Resource Identifiers (URIs) [RFC3986] to
   identify resources, algorithms, and semantics.

1.3.1.  Defined Identifiers

   The XML namespace [XMLNS] URI for Version 1.0 of PSKC is:

   "urn:ietf:params:xml:ns:keyprov:pskc"

   References to qualified elements in the PSKC schema defined in this
   specification and used in the example use the prefix "pskc" (defined
   as xmlns:pskc="urn:ietf:params:xml:ns:keyprov:pskc").  It is
   RECOMMENDED to use this namespace in implementations.

1.3.2.  Referenced Identifiers

   The PSKC syntax presented in this document relies on algorithm
   identifiers and elements defined in the XML Signature [XMLDSIG]
   namespace:

   xmlns:ds="http://www.w3.org/2000/09/xmldsig#"

   References to the XML Signature namespace are represented by the
   prefix "ds".

   PSKC also relies on algorithm identifiers and elements defined in the
   XML Encryption [XMLENC] namespace:

   xmlns:xenc="http://www.w3.org/2001/04/xmlenc#"

   References to the XML Encryption namespace are represented by the
   prefix "xenc".

   When protecting keys in transport with passphrase-based keys, PSKC
   also relies on the derived key element defined in the XML Encryption
   Version 1.1 [XMLENC11] namespace:

   xmlns:xenc11="http://www.w3.org/2009/xmlenc11#"

   References to the XML Encryption Version 1.1 namespace are
   represented by the prefix "xenc11".

   When protecting keys in transport with passphrase-based keys, PSKC
   also relies on algorithm identifiers and elements defined in the PKCS
   #5 [PKCS5] namespace:




Hoyer, et al.                Standards Track                    [Page 5]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   xmlns:pkcs5=
   "http://www.rsasecurity.com/rsalabs/pkcs/schemas/pkcs-5v2-0#"

   References to the PKCS #5 namespace are represented by the prefix
   "pkcs5".

2.  Terminology

   NOTE: In subsequent sections of the document, we highlight
   **mandatory** XML elements and attributes.  Optional elements and
   attributes are not explicitly indicated, i.e., if it does not say
   mandatory, it is optional.

3.  Portable Key Container Entities Overview and Relationships

   The portable key container is based on an XML schema definition and
   contains the following main conceptual entities:

   1.  KeyContainer entity - representing the container that carries a
       number of KeyPackage entities.  A valid container MUST carry at
       least one KeyPackage entity.

   2.  KeyPackage entity - representing the package of at most one key
       and its related provisioning endpoint or current usage endpoint,
       such as a physical or virtual device and a specific CryptoModule.

   3.  DeviceInfo entity - representing the information about the device
       and criteria to identify uniquely the device.

   4.  CryptoModuleInfo entity - representing the information about the
       CryptoModule where the keys reside or to which they are
       provisioned.

   5.  Key entity - representing the key transported or provisioned.

   6.  Data entity - representing a list of metadata related to the key,
       where the element name is the name of the metadata and its
       associated value is either in encrypted (for example, for <Data>
       element <Secret>) or plaintext (for example, the <Data> element
       <Counter>) form.

   Figure 1 shows the high-level structure of the PSKC data elements.









Hoyer, et al.                Standards Track                    [Page 6]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


      -----------------
      | KeyContainer  |
      |---------------|
      | EncryptionKey |
      | Signature     |
      | ...           |
      -----------------
              |
              |
             /|\ 1..n
      ----------------        ----------------
      | KeyPackage   |    0..1| DeviceInfo   |
      |--------------|--------|--------------|
      |              |--      | SerialNumber |
      ----------------  |     | Manufacturer |
              |         |     | ....         |
              |         |     ----------------
             /|\ 0..1   |
      ----------------  |     --------------------
      | Key          |  | 0..1| CryptoModuleInfo |
      |--------------|   -----|------------------|
      | Id           |        | Id               |
      | Algorithm    |        |....              |
      | UserId       |        --------------------
      | Policy       |
      | ....         |
      ----------------
              |
              |
             /|\ 0..n
          --------------------------------------- -  -
          |                     |              |
      ------------------  ----------------  -------- - -
      | Data:Secret    |  | Data:Counter |  | Data:other
      |----------------|  |--------------|  |-- - -
      | EncryptedValue |  | PlainValue   |
      | ValueMAC       |  ----------------
      ------------------

             Figure 1: PSKC Data Elements Relationship Diagram

   The following sections describe in detail all the entities and
   related XML schema elements and attributes.








Hoyer, et al.                Standards Track                    [Page 7]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


4.  <KeyContainer> Element: The Basics

   In its most basic form, a PSKC document uses the top-level element
   <KeyContainer> and a single <KeyPackage> element to carry key
   information.

   The following example shows a simple PSKC document.  We will use it
   to describe the structure of the <KeyContainer> element and its child
   elements.

   <?xml version="1.0" encoding="UTF-8"?>
   <KeyContainer Version="1.0"
       Id="exampleID1"
       xmlns="urn:ietf:params:xml:ns:keyprov:pskc">
       <KeyPackage>
           <Key Id="12345678"
               Algorithm="urn:ietf:params:xml:ns:keyprov:pskc:hotp">
               <Issuer>Issuer-A</Issuer>
               <Data>
                   <Secret>
                       <PlainValue>MTIzNA==
                       </PlainValue>
                   </Secret>
               </Data>
           </Key>
       </KeyPackage>
   </KeyContainer>

                Figure 2: Basic PSKC Key Container Example

   The attributes of the <KeyContainer> element have the following
   semantics:

   'Version':  The 'Version' attribute is used to identify the version
      of the PSKC schema version.  This specification defines the
      initial version ("1.0") of the PSKC schema.  This attribute MUST
      be included.

   'Id':  The 'Id' attribute carries a unique identifier for the
      container.  As such, it helps to identify a specific key container
      in cases in which multiple containers are embedded in larger XML
      documents.

4.1.  <Key>: Embedding Keying Material and Key-Related Information

   The following attributes of the <Key> element MUST be included at a
   minimum:




Hoyer, et al.                Standards Track                    [Page 8]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   'Id':  This attribute carries a unique identifier for the symmetric
      key in the context of key provisioning exchanges between two
      parties.  This means that if PSKC is used in multiple interactions
      between a sending and receiving party, using different containers
      referencing the same keys, the 'Id' attribute of <Key> MUST use
      the same value (e.g., after initial provisioning, if a system
      wants to update key metadata values in the other system, the value
      of the 'Id' attribute of the <Key> where the metadata is to be
      updated MUST be the same of the original 'Id' attribute value
      provisioned).  The identifier is defined as a string of
      alphanumeric characters.

   'Algorithm':  This attribute contains a unique identifier for the
      PSKC algorithm profile.  This profile associates specific
      semantics to the elements and attributes contained in the <Key>
      element.  This document describes profiles for open standards
      algorithms in Section 10.  Additional profiles are defined in the
      following informative document: [PSKC-ALGORITHM-PROFILES].

   The <Key> element has a number of optional child elements.  An
   initial set is described below:

   <Issuer>:  This element represents the name of the party that issued
      the key.  For example, a bank "Foobar Bank, Inc." issuing hardware
      tokens to their retail banking users may set this element to
      'Foobar Bank, Inc.'.

   <FriendlyName>:  A human-readable name for the secret key for easier
      reference.  This element serves informational purposes only.  This
      element is a language-dependent string; hence, it SHOULD have an
      attribute xml:lang="xx" where xx is the language identifier as
      specified in [RFC5646].  If no xml:lang attribute is present,
      implementations MUST assume the language to be English as defined
      by setting the attribute value to 'en' (e.g., xml:lang="en").

   <AlgorithmParameters>:  This element carries parameters that
      influence the result of the algorithmic computation, for example,
      response truncation and format in OTP and CR algorithms.  A more
      detailed discussion of the element can be found in Section 4.3.4.

   <Data>:  This element carries data about and related to the key.  The
      following child elements are defined for the <Data> element:

      <Secret>:  This element carries the value of the key itself in a
         binary representation.  Please see Section 4.2 for more details
         on Key Value Encoding.





Hoyer, et al.                Standards Track                    [Page 9]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


      <Counter>:  This element contains the event counter for event-
         based OTP algorithms.

      <Time>:  This element contains the time for time-based OTP
         algorithms.  (If time intervals are used, this element carries
         the number of time intervals passed from a specific start
         point, normally it is algorithm dependent).

      <TimeInterval>:  This element carries the time interval value for
         time-based OTP algorithms in seconds (a typical value for this
         would be 30, indicating a time interval of 30 seconds).

      <TimeDrift>:  This element contains the device clock drift value
         for time-based OTP algorithms.  The integer value (positive or
         negative drift) that indicates the number of time intervals
         that a validation server has established the device clock
         drifted after the last successful authentication.  So, for
         example, if the last successful authentication established a
         device time value of 8 intervals from a specific start date but
         the validation server determines the time value at 9 intervals,
         the server SHOULD record the drift as -1.

      All the elements listed above (and those defined in the future)
      obey a simple structure in that they MUST support child elements
      to convey the data value in either plaintext or encrypted format:

      Plaintext:  The <PlainValue> element carries a plaintext value
         that is typed, for example, to xs:integer.

      Encrypted:  The <EncryptedValue> element carries an encrypted
         value.

      ValueMAC:  The <ValueMAC> element is populated with a Message
         Authentication Code (MAC) generated from the encrypted value in
         case the encryption algorithm does not support integrity
         checks.  The example shown in Figure 2 illustrates the usage of
         the <Data> element with two child elements, namely <Secret> and
         <Counter>.  Both elements carry a plaintext value within the
         <PlainValue> child element.

4.2.  Key Value Encoding

   Two parties receiving the same key value OCTET STRING, resulting in
   decoding the xs:base64Binary, inside the <PlainValue> or
   <EncryptedValue> elements, must make use of the key in exactly the
   same way in order to interoperate.  To ensure that, it is necessary
   to define a correspondence between the OCTET STRING and the notation
   in the standard algorithm description that defines how the key is



Hoyer, et al.                Standards Track                   [Page 10]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   used.  The next sections establish that correspondence for the AES
   algorithm [FIPS197] and the Triple Data Encryption Algorithm (TDEA or
   Triple DES) [SP800-67].  Unless otherwise specified for a specific
   algorithm, the OCTET STRING encoding MUST follow the AES Key Value
   Encoding.

4.2.1.  AES Key Value Encoding

   [FIPS197], Section 5.2, titled "Key Expansion", uses the input key as
   an array of bytes indexed starting at 0.  The first octet of the
   OCTET STRING SHALL become the key byte in the AES, labeled index 0 in
   [FIPS197]; the succeeding octets of the OCTET STRING SHALL become key
   bytes in AES, in increasing index order.

   Proper parsing and key load of the contents of the OCTET STRING for
   AES SHALL be determined by using the following value for the
   <PlainValue> element (binaryBase64-encoded) to generate and match the
   key expansion test vectors in [FIPS197], Appendix A, for AES

   Cipher Key: 2b 7e 15 16 28 ae d2 a6 ab f7 15 88 09 cf 4f 3c

   ...
    <PlainValue>K34VFiiu0qar9xWICc9PPA==</PlainValue>
   ...

4.2.2.  Triple-DES Key Value Encoding

   A Triple-DES key consists of three keys for the cryptographic engine
   (Key1, Key2, and Key3) that are each 64 bits (56 key bits and 8
   parity bits); the three keys are also collectively referred to as a
   key bundle [SP800-67].  A key bundle may employ either two or three
   independent keys.  When only two independent keys are employed
   (called two-key Triple DES), the same value is used for Key1 and
   Key3.

   Each key in a Triple-DES key bundle is expanded into a key schedule
   according to a procedure defined in [SP800-67], Appendix A.  That
   procedure numbers the bits in the key from 1 to 64, with number 1
   being the leftmost, or most significant bit (MSB).  The first octet
   of the OCTET STRING SHALL be bits 1 through 8 of Key1 with bit 1
   being the MSB.  The second octet of the OCTET STRING SHALL be bits 9
   through 16 of Key1, and so forth, so that the trailing octet of the
   OCTET STRING SHALL be bits 57 through 64 of Key3 (or Key2 for two-key
   Triple DES).







Hoyer, et al.                Standards Track                   [Page 11]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   Proper parsing and key load of the contents of the OCTET STRING for
   Triple DES SHALL be determined by using the following <PlainValue>
   element (binaryBase64-encoded) to generate and match the key
   expansion test vectors in [SP800-67], Appendix B, for the key bundle:

   Key1 = 0123456789ABCDEF

   Key2 = 23456789ABCDEF01

   Key3 = 456789ABCDEF0123

   ...
    <PlainValue>ASNFZ4mrze8jRWeJq83vAUVniavN7wEj</PlainValue>
   ...

4.3.  Transmission of Supplementary Information

   A PSKC document can contain a number of additional information
   regarding device identification, cryptographic module identification,
   user identification, and parameters for usage with OTP and CR
   algorithms.  The following example, see Figure 3, is used as a
   reference for the subsequent sub-sections.





























Hoyer, et al.                Standards Track                   [Page 12]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   <?xml version="1.0" encoding="UTF-8"?>
   <KeyContainer Version="1.0"
       Id="exampleID1"
       xmlns="urn:ietf:params:xml:ns:keyprov:pskc">
       <KeyPackage>
           <DeviceInfo>
               <Manufacturer>Manufacturer</Manufacturer>
               <SerialNo>987654321</SerialNo>
               <UserId>DC=example-bank,DC=net</UserId>
           </DeviceInfo>
           <CryptoModuleInfo>
               <Id>CM_ID_001</Id>
           </CryptoModuleInfo>
           <Key Id="12345678"
               Algorithm="urn:ietf:params:xml:ns:keyprov:pskc:hotp">
               <Issuer>Issuer</Issuer>
               <AlgorithmParameters>
                   <ResponseFormat Length="8" Encoding="DECIMAL"/>
               </AlgorithmParameters>
               <Data>
                   <Secret>
                       <PlainValue>MTIzNDU2Nzg5MDEyMzQ1Njc4OTA=
                       </PlainValue>
                   </Secret>
                   <Counter>
                       <PlainValue>0</PlainValue>
                   </Counter>
               </Data>
               <UserId>UID=jsmith,DC=example-bank,DC=net</UserId>
           </Key>
       </KeyPackage>
   </KeyContainer>

       Figure 3: PSKC Key Container Example with Supplementary Data

4.3.1.  <DeviceInfo> Element: Unique Device Identification

   The <DeviceInfo> element uniquely identifies the device to which the
   <KeyPackage> is provisioned.  Since devices can come in different
   form factors, such as hardware tokens, smart-cards, soft tokens in a
   mobile phone, or as a PC, this element allows different child element
   combinations to be used.  When combined, the values of the child
   elements MUST uniquely identify the device.  For example, for
   hardware tokens, the combination of <SerialNo> and <Manufacturer>
   elements uniquely identifies a device, but the <SerialNo> element
   alone is insufficient since two different token manufacturers might
   issue devices with the same serial number (similar to the Issuer
   Distinguished Name and serial number of a certificate).



Hoyer, et al.                Standards Track                   [Page 13]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   The <DeviceInfo> element has the following child elements:

   <Manufacturer>:  This element indicates the manufacturer of the
      device.  Values for the <Manufacturer> element MUST be taken from
      either [OATHMAN] prefixes (i.e., the left column) or from the IANA
      Private Enterprise Number Registry [IANAPENREG], using the
      Organization value.  When the value is taken from [OATHMAN],
      "oath."  MUST be prepended to the value (e.g., "oath.<prefix value
      from [OATHMAN]>").  When the value is taken from [IANAPENREG],
      "iana."  MUST be prepended to the value (e.g., "iana.<Organization
      value from [IANAPENREG]>").

   <SerialNo>:  This element contains the serial number of the device.

   <Model>:  This element describes the model of the device (e.g., one-
      button-HOTP-token-V1).

   <IssueNo>:  This element contains the issue number in case there are
      devices with the same serial number so that they can be
      distinguished by different issue numbers.

   <DeviceBinding>:  This element allows a provisioning server to ensure
      that the key is going to be loaded into the device for which the
      key provisioning request was approved.  The device is bound to the
      request using a device identifier, e.g., an International Mobile
      Equipment Identity (IMEI) for the phone, or an identifier for a
      class of identifiers, e.g., those for which the keys are protected
      by a Trusted Platform Module (TPM).

   <StartDate> and <ExpiryDate>:  These two elements indicate the start
      and end date of a device (such as the one on a payment card, used
      when issue numbers are not printed on cards).  The date MUST be
      expressed as a dateTime value in "canonical representation"
      [W3C.REC-xmlschema-2-20041028].  Implementations SHOULD NOT rely
      on time resolution finer than milliseconds and MUST NOT generate
      time instants that specify leap seconds.  Keys that reside on the
      device SHOULD only be used when the current date is after the
      <StartDate> and before the <ExpiryDate>.  Note that usage
      enforcement of the keys with respect to the dates MAY only happen
      on the validation server, as some devices such as smart cards do
      not have an internal clock.  Systems thus SHOULD NOT rely upon the
      device to enforce key usage date restrictions.

   Depending on the device type, certain child elements of the
   <DeviceInfo> element MUST be included in order to uniquely identify a
   device.  This document does not enumerate the different device types
   and therefore does not list the elements that are mandatory for each
   type of device.



Hoyer, et al.                Standards Track                   [Page 14]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


4.3.2.  <CryptoModuleInfo> Element: CryptoModule Identification

   The <CryptoModuleInfo> element identifies the cryptographic module to
   which the symmetric keys are or have been provisioned.  This allows
   the identification of the specific cases where a device MAY contain
   more than one crypto module (e.g., a PC hosting a TPM and a connected
   token).

   The <CryptoModuleInfo> element has a single child element that MUST
   be included:

   <Id>:  This element carries a unique identifier for the CryptoModule
      and is implementation specific.  As such, it helps to identify a
      specific CryptoModule to which the key is being or was
      provisioned.

4.3.3.  <UserId> Element: User Identification

   The <UserId> element identifies the user of a distinguished name, as
   defined in [RFC4514], for example, UID=jsmith,DC=example,DC=net.

   Although the syntax of the user identifier is defined, there are no
   semantics associated with this element, i.e., there are no checks
   enforcing that only a specific user can use this key.  As such, this
   element is for informational purposes only.

   This element may appear in two places, namely as a child element of
   the <Key> element, where it indicates the user with whom the key is
   associated, and as a child element of the <DeviceInfo> element, where
   it indicates the user with whom the device is associated.

4.3.4.  <AlgorithmParameters> Element: Supplementary Information for OTP
        and CR Algorithms

   The <AlgorithmParameters> element is a child element of the <Key>
   element, and this document defines three child elements: <Suite>,
   <ChallengeFormat>, and <ResponseFormat>.

   <Suite>:

      The optional <Suite> element defines additional characteristics of
      the algorithm used, which are algorithm specific.  For example, in
      an HMAC-based (Hashed MAC) OTP algorithm, it could designate the
      strength of the hash algorithm used (SHA1, SHA256, etc.).  Please
      refer to the algorithm profile section, Section 10, for the exact
      semantics of the value for each algorithm profile.





Hoyer, et al.                Standards Track                   [Page 15]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   <ChallengeFormat>:

      The <ChallengeFormat> element defines the characteristics of the
      challenge in a CR usage scenario whereby the following attributes
      are defined:

      'Encoding':  This attribute, which MUST be included, defines the
         encoding of the challenge accepted by the device and MUST be
         one of the following values:

         DECIMAL:  Only numerical digits

         HEXADECIMAL:  Hexadecimal response

         ALPHANUMERIC:  All letters and numbers (case sensitive)

         BASE64:  Base-64 encoded, as defined in Section 4 of [RFC4648]

         BINARY:  Binary data

      'CheckDigit':  This attribute indicates whether a device needs to
         check the appended Luhn check digit, as defined in
         [ISOIEC7812], contained in a challenge.  This is only valid if
         the 'Encoding' attribute is set to 'DECIMAL'.  A value of TRUE
         indicates that the device will check the appended Luhn check
         digit in a provided challenge.  A value of FALSE indicates that
         the device will not check the appended Luhn check digit in the
         challenge.

      'Min':  This attribute defines the minimum size of the challenge
         accepted by the device for CR mode and MUST be included.  If
         the 'Encoding' attribute is set to 'DECIMAL', 'HEXADECIMAL', or
         'ALPHANUMERIC', this value indicates the minimum number of
         digits/characters.  If the 'Encoding' attribute is set to
         'BASE64' or 'BINARY', this value indicates the minimum number
         of bytes of the unencoded value.

      'Max':  This attribute defines the maximum size of the challenge
         accepted by the device for CR mode and MUST be included.  If
         the 'Encoding' attribute is set to 'DECIMAL', 'HEXADECIMAL', or
         'ALPHANUMERIC', this value indicates the maximum number of
         digits/characters.  If the 'Encoding' attribute is set to
         'BASE64' or 'BINARY', this value indicates the maximum number
         of bytes of the unencoded value.







Hoyer, et al.                Standards Track                   [Page 16]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   <ResponseFormat>:

      The <ResponseFormat> element defines the characteristics of the
      result of a computation and defines the format of the OTP or the
      response to a challenge.  For cases in which the key is a PIN
      value, this element contains the format of the PIN itself (e.g.,
      DECIMAL, length 4 for a 4-digit PIN).  The following attributes
      are defined:

      'Encoding':  This attribute defines the encoding of the response
         generated by the device, it MUST be included and MUST be one of
         the following values: DECIMAL, HEXADECIMAL, ALPHANUMERIC,
         BASE64, or BINARY.

      'CheckDigit':  This attribute indicates whether the device needs
         to append a Luhn check digit, as defined in [ISOIEC7812], to
         the response.  This is only valid if the 'Encoding' attribute
         is set to 'DECIMAL'.  If the value is TRUE, then the device
         will append a Luhn check digit to the response.  If the value
         is FALSE, then the device will not append a Luhn check digit to
         the response.

      'Length':  This attribute defines the length of the response
         generated by the device and MUST be included.  If the
         'Encoding' attribute is set to 'DECIMAL', 'HEXADECIMAL', or
         ALPHANUMERIC, this value indicates the number of digits/
         characters.  If the 'Encoding' attribute is set to 'BASE64' or
         'BINARY', this value indicates the number of bytes of the
         unencoded value.

4.4.  Transmission of Key Derivation Values

   <KeyProfileId> element, which is a child element of the <Key>
   element, carries a unique identifier used between the sending and
   receiving parties to establish a set of key attribute values that are
   not transmitted within the container but are agreed upon between the
   two parties out of band.  This element will then represent the unique
   reference to a set of key attribute values.  (For example, a smart
   card application personalization profile id related to specific
   attribute values present on a smart card application that have
   influence when computing a response).

   For example, in the case of MasterCard's Chip Authentication Program
   [CAP], the sending and the receiving party would agree that
   KeyProfileId='1' represents a certain set of values (e.g., Internet
   Authentication Flag (IAF) set to a specific value).  During
   transmission of the <KeyContainer>, these values would not be
   transmitted as key attributes but would only be referred to via the



Hoyer, et al.                Standards Track                   [Page 17]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   <KeyProfileId> element set to the specific agreed-upon profile (in
   this case '1').  The receiving party can then associate all relevant
   key attributes contained in the profile that was agreed upon out of
   band with the imported keys.  Often, this methodology is used between
   a manufacturing service, run by company A, and the validation
   service, run by company B, to avoid repeated transmission of the same
   set of key attribute values.

   The <KeyReference> element contains a reference to an external key to
   be used with a key derivation scheme.  In this case, the parent <Key>
   element will not contain the <Secret> subelement of <Data>, in which
   the key value (secret) is transported; only the reference to the
   external master key is transported (e.g., a PKCS #11 key label).

   <?xml version="1.0" encoding="UTF-8"?>
   <KeyContainer Version="1.0" Id="exampleID1"
        xmlns="urn:ietf:params:xml:ns:keyprov:pskc">
       <KeyPackage>
           <DeviceInfo>
               <Manufacturer>Manufacturer</Manufacturer>
               <SerialNo>987654321</SerialNo>
           </DeviceInfo>
           <CryptoModuleInfo>
               <Id>CM_ID_001</Id>
           </CryptoModuleInfo>
           <Key Id="12345678"
            Algorithm="urn:ietf:params:xml:ns:keyprov:pskc:hotp">
               <Issuer>Issuer</Issuer>
               <AlgorithmParameters>
                   <ResponseFormat Length="8" Encoding="DECIMAL"/>
               </AlgorithmParameters>
               <KeyProfileId>keyProfile1</KeyProfileId>
               <KeyReference>MasterKeyLabel
               </KeyReference>
               <Data>
                   <Counter>
                       <PlainValue>0</PlainValue>
                   </Counter>
               </Data>
               <Policy>
                   <KeyUsage>OTP</KeyUsage>
               </Policy>
           </Key>
       </KeyPackage>
   </KeyContainer>

   Figure 4: Example of a PSKC Document Transmitting an HOTP Key via Key
                             Derivation Values



Hoyer, et al.                Standards Track                   [Page 18]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   The key value will be derived using the value of the <SerialNo>
   element, values agreed upon between the sending and the receiving
   parties and identified by the <KeyProfile> 'keyProfile1', and an
   externally agreed-upon key referenced by the label 'MasterKeyLabel'.

5.  Key Policy

   This section illustrates the functionality of the <Policy> element
   within PSKC, which allows a key usage and key PIN protection policy
   to be attached to a specific key and its related metadata.  This
   element is a child element of the <Key> element.

   If the <Policy> element contains child elements or values within
   elements/attributes that are not understood by the recipient of the
   PSKC document, then the recipient MUST assume that key usage is not
   permitted.  This statement ensures that the lack of understanding of
   certain extensions does not lead to unintended key usage.

   We will start our description with an example that expands the
   example shown in Figure 3.

   <?xml version="1.0" encoding="UTF-8"?>
   <KeyContainer
       Version="1.0" Id="exampleID1"
       xmlns="urn:ietf:params:xml:ns:keyprov:pskc">
       <KeyPackage>
           <DeviceInfo>
               <Manufacturer>Manufacturer</Manufacturer>
               <SerialNo>987654321</SerialNo>
           </DeviceInfo>
           <CryptoModuleInfo>
               <Id>CM_ID_001</Id>
           </CryptoModuleInfo>
           <Key Id="12345678"
               Algorithm="urn:ietf:params:xml:ns:keyprov:pskc:hotp">
               <Issuer>Issuer</Issuer>
               <AlgorithmParameters>
                   <ResponseFormat Length="8" Encoding="DECIMAL"/>
               </AlgorithmParameters>
               <Data>
                   <Secret>
                       <PlainValue>MTIzNDU2Nzg5MDEyMzQ1Njc4OTA=
                       </PlainValue>
                   </Secret>
                   <Counter>
                       <PlainValue>0</PlainValue>





Hoyer, et al.                Standards Track                   [Page 19]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


                   </Counter>
               </Data>
               <Policy>
                   <PINPolicy MinLength="4" MaxLength="4"
                       PINKeyId="123456781" PINEncoding="DECIMAL"
                       PINUsageMode="Local"/>
                   <KeyUsage>OTP</KeyUsage>
               </Policy>
           </Key>
       </KeyPackage>
       <KeyPackage>
           <DeviceInfo>
               <Manufacturer>Manufacturer</Manufacturer>
               <SerialNo>987654321</SerialNo>
           </DeviceInfo>
           <CryptoModuleInfo>
               <Id>CM_ID_001</Id>
           </CryptoModuleInfo>
           <Key Id="123456781"
               Algorithm="urn:ietf:params:xml:ns:keyprov:pskc:pin">
               <Issuer>Issuer</Issuer>
               <AlgorithmParameters>
                   <ResponseFormat Length="4" Encoding="DECIMAL"/>
               </AlgorithmParameters>
               <Data>
                   <Secret>
                       <PlainValue>MTIzNA==</PlainValue>
                   </Secret>
               </Data>
           </Key>
       </KeyPackage>
   </KeyContainer>

         Figure 5: Non-Encrypted HOTP Secret Key Protected by PIN

   This document defines the following <Policy> child elements:

   <StartDate> and <ExpiryDate>:  These two elements denote the validity
      period of a key.  It MUST be ensured that the key is only used
      between the start and the end date (inclusive).  The date MUST be
      expressed as a dateTime value in "canonical representation"
      [W3C.REC-xmlschema-2-20041028].  Implementations SHOULD NOT rely
      on time resolution finer than milliseconds and MUST NOT generate
      time instants that specify leap seconds.  When this element is
      absent, the current time is assumed as the start time.






Hoyer, et al.                Standards Track                   [Page 20]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   <NumberOfTransactions>:  The value in this element indicates the
      maximum number of times a key carried within the PSKC document can
      be used by an application after having received it.  When this
      element is omitted, there is no restriction regarding the number
      of times a key can be used.

   <KeyUsage>:  The <KeyUsage> element puts constraints on the intended
      usage of the key.  The recipient of the PSKC document MUST enforce
      the key usage.  Currently, the following tokens are registered by
      this document:

      OTP:  The key MUST only be used for OTP generation.

      CR:  The key MUST only be used for Challenge/Response purposes.

      Encrypt:  The key MUST only be used for data encryption purposes.

      Integrity:  The key MUST only be used to generate a keyed message
         digest for data integrity or authentication purposes.

      Verify:  The key MUST only be used to verify a keyed message
         digest for data integrity or authentication purposes (this is
         the opposite key usage of 'Integrity').

      Unlock:  The key MUST only be used for an inverse Challenge/
         Response in the case where a user has locked the device by
         entering a wrong PIN too many times (for devices with PIN-input
         capability).

      Decrypt:  The key MUST only be used for data decryption purposes.

      KeyWrap:  The key MUST only be used for key wrap purposes.

      Unwrap:  The key MUST only be used for key unwrap purposes.

      Derive:  The key MUST only be used with a key derivation function
         to derive a new key (see also Section 8.2.4 of [NIST800-57]).

      Generate:  The key MUST only be used to generate a new key based
         on a random number and the previous value of the key (see also
         Section 8.1.5.2.1 of [NIST800-57]).

      The element MAY also be repeated to allow several key usages to be
      expressed.  When this element is absent, no key usage constraint
      is assumed, i.e., the key MAY be utilized for every usage.






Hoyer, et al.                Standards Track                   [Page 21]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   <PINPolicy>:  The <PINPolicy> element allows policy about the PIN
      usage to be associated with the key.  The following attributes are
      specified:

      'PINKeyId':  This attribute carries the unique 'Id' attribute vale
         of the <Key> element held within this <KeyContainer> that
         contains the value of the PIN that protects the key.

      'PINUsageMode':  This mandatory attribute indicates the way the
         PIN is used during the usage of the key.  The following values
         are defined:

         Local:  This value indicates that the PIN is checked locally on
            the device before allowing the key to be used in executing
            the algorithm.

         Prepend:  This value indicates that the PIN is prepended to the
            algorithm response; hence, it MUST be checked by the party
            validating the response.

         Append:  This value indicates that the PIN is appended to the
            algorithm response; hence, it MUST be checked by the party
            validating the response.

         Algorithmic:  This value indicates that the PIN is used as part
            of the algorithm computation.

      'MaxFailedAttempts':  This attribute indicates the maximum number
         of times the PIN may be entered wrongly before it MUST NOT be
         possible to use the key anymore (typical reasonable values are
         in the positive integer range of at least 2 and no more than
         10).

      'MinLength':  This attribute indicates the minimum length of a PIN
         that can be set to protect the associated key.  It MUST NOT be
         possible to set a PIN shorter than this value.  If the
         'PINFormat' attribute is set to 'DECIMAL', 'HEXADECIMAL', or
         'ALPHANUMERIC', this value indicates the number of digits/
         characters.  If the 'PINFormat' attribute is set to 'BASE64' or
         'BINARY', this value indicates the number of bytes of the
         unencoded value.

      'MaxLength':  This attribute indicates the maximum length of a PIN
         that can be set to protect this key.  It MUST NOT be possible
         to set a PIN longer than this value.  If the 'PINFormat'
         attribute is set to 'DECIMAL', 'HEXADECIMAL', or
         'ALPHANUMERIC', this value indicates the number of digits/




Hoyer, et al.                Standards Track                   [Page 22]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


         characters.  If the 'PINFormat' attribute is set to 'BASE64' or
         'BINARY', this value indicates the number of bytes of the
         unencoded value.

      'PINEncoding':  This attribute indicates the encoding of the PIN
         and MUST be one of the values: DECIMAL, HEXADECIMAL,
         ALPHANUMERIC, BASE64, or BINARY.

      If the 'PinUsageMode' attribute is set to 'Local', then the device
      MUST enforce the restriction indicated in the 'MaxFailedAttempts',
      'MinLength', 'MaxLength', and 'PINEncoding' attributes; otherwise,
      it MUST be enforced on the server side.

5.1.  PIN Algorithm Definition

   The PIN algorithm is defined as:

   boolean = comparePIN(K,P)

   Where:

      'K' is the stored symmetric credential (PIN) in binary format.

      'P' is the proposed PIN to be compared in binary format.

   The function comparePIN is a straight octet comparison of K and P.
   Such a comparison MUST yield a value of TRUE (credentials matched)
   when the octet length of K is the same as the octet length of P and
   all octets comprising K are the same as the octets comprising P.

6.  Key Protection Methods

   With the functionality described in the previous sections,
   information related to keys had to be transmitted in cleartext.  With
   the help of the <EncryptionKey> element, which is a child element of
   the <KeyContainer> element, it is possible to encrypt keys and
   associated information.  The level of encryption is applied to the
   value of individual elements and the applied encryption algorithm
   MUST be the same for all encrypted elements.  Keys are protected
   using the following methods: pre-shared keys, passphrase-based keys,
   and asymmetric keys.  When encryption algorithms are used that make
   use of Initialization Vectors (IVs), for example, AES-128-CBC, a
   random IV value MUST be generated for each value to be encrypted and
   it MUST be prepended to the resulting encrypted value as specified in
   [XMLENC].






Hoyer, et al.                Standards Track                   [Page 23]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


6.1.  Encryption Based on Pre-Shared Keys

   Figure 6 shows an example that illustrates the encryption of the
   content of the <Secret> element using AES-128-CBC and PKCS #5
   Padding.  The plaintext value of <Secret> is
   '3132333435363738393031323334353637383930'.  The name of the pre-
   shared secret is "Pre-shared-key", as set in the <KeyName> element
   (which is a child element of the <EncryptionKey> element).  The value
   of the encryption key used is '12345678901234567890123456789012'.

   The IV for the MAC key is '11223344556677889900112233445566', and the
   IV for the HOTP key is '000102030405060708090a0b0c0d0e0f'.

   As AES-128-CBC does not provide integrity checks, a keyed MAC is
   applied to the encrypted value using a MAC key and a MAC algorithm as
   declared in the <MACMethod> element (in our example,
   "http://www.w3.org/2000/09/xmldsig#hmac-sha1" is used as the
   algorithm and the value of the MAC key is randomly generated, in our
   case '1122334455667788990011223344556677889900', and encrypted with
   the above encryption key).  The result of the keyed-MAC computation
   is placed in the <ValueMAC> child element of <Secret>.

 <?xml version="1.0" encoding="UTF-8"?>
 <KeyContainer Version="1.0"
     xmlns="urn:ietf:params:xml:ns:keyprov:pskc"
     xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
     xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
     <EncryptionKey>
         <ds:KeyName>Pre-shared-key</ds:KeyName>
     </EncryptionKey>
     <MACMethod Algorithm="http://www.w3.org/2000/09/xmldsig#hmac-sha1">
         <MACKey>
             <xenc:EncryptionMethod
             Algorithm="http://www.w3.org/2001/04/xmlenc#aes128-cbc"/>
             <xenc:CipherData>
                 <xenc:CipherValue>
     ESIzRFVmd4iZABEiM0RVZgKn6WjLaTC1sbeBMSvIhRejN9vJa2BOlSaMrR7I5wSX
                 </xenc:CipherValue>
             </xenc:CipherData>
         </MACKey>
     </MACMethod>
     <KeyPackage>
         <DeviceInfo>
             <Manufacturer>Manufacturer</Manufacturer>
             <SerialNo>987654321</SerialNo>
         </DeviceInfo>
         <CryptoModuleInfo>




Hoyer, et al.                Standards Track                   [Page 24]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


             <Id>CM_ID_001</Id>
         </CryptoModuleInfo>
         <Key Id="12345678"
             Algorithm="urn:ietf:params:xml:ns:keyprov:pskc:hotp">
             <Issuer>Issuer</Issuer>
             <AlgorithmParameters>
                 <ResponseFormat Length="8" Encoding="DECIMAL"/>
             </AlgorithmParameters>
             <Data>
                 <Secret>
                     <EncryptedValue>
                         <xenc:EncryptionMethod
             Algorithm="http://www.w3.org/2001/04/xmlenc#aes128-cbc"/>
                         <xenc:CipherData>
                             <xenc:CipherValue>
     AAECAwQFBgcICQoLDA0OD+cIHItlB3Wra1DUpxVvOx2lef1VmNPCMl8jwZqIUqGv
                             </xenc:CipherValue>
                         </xenc:CipherData>
                     </EncryptedValue>
                     <ValueMAC>Su+NvtQfmvfJzF6bmQiJqoLRExc=
                     </ValueMAC>
                 </Secret>
                 <Counter>
                     <PlainValue>0</PlainValue>
                 </Counter>
             </Data>
         </Key>
     </KeyPackage>
 </KeyContainer>

   Figure 6: AES-128-CBC Encrypted Pre-Shared Secret Key with HMAC-SHA1

   When protecting the payload with pre-shared keys, implementations
   MUST set the name of the specific pre-shared key in the <KeyName>
   element inside the <EncryptionKey> element.  When the encryption
   method uses a CBC mode that requires an explicit initialization
   vector (IV), the IV MUST be passed by prepending it to the encrypted
   value.

   For systems implementing PSKC, it is RECOMMENDED to support
   AES-128-CBC (with the URI of
   http://www.w3.org/2001/04/xmlenc#aes128-cbc) and KW-AES128 (with the
   URI of http://www.w3.org/2001/04/xmlenc#kw-aes128).  Please note that
   KW-AES128 requires that the key to be protected must be a multiple of
   8 bytes in length.  Hence, if keys of a different length have to be
   protected, then the usage of the key-wrap algorithm with padding, as
   described in [RFC5649] is RECOMMENDED.  Some of the encryption
   algorithms that can optionally be implemented are:



Hoyer, et al.                Standards Track                   [Page 25]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


 Algorithm      | Uniform Resource Locator (URL)
 ---------------+-------------------------------------------------------
 AES192-CBC     | http://www.w3.org/2001/04/xmlenc#aes192-cbc
 AES256-CBC     | http://www.w3.org/2001/04/xmlenc#aes256-cbc
 TripleDES-CBC  | http://www.w3.org/2001/04/xmlenc#tripledes-cbc
 Camellia128    | http://www.w3.org/2001/04/xmldsig-more#camellia128
 Camellia192    | http://www.w3.org/2001/04/xmldsig-more#camellia192
 Camellia256    | http://www.w3.org/2001/04/xmldsig-more#camellia256
 KW-AES128      | http://www.w3.org/2001/04/xmlenc#kw-aes128
 KW-AES192      | http://www.w3.org/2001/04/xmlenc#kw-aes192
 KW-AES256      | http://www.w3.org/2001/04/xmlenc#kw-aes256
 KW-TripleDES   | http://www.w3.org/2001/04/xmlenc#kw-tripledes
 KW-Camellia128 | http://www.w3.org/2001/04/xmldsig-more#kw-camellia128
 KW-Camellia192 | http://www.w3.org/2001/04/xmldsig-more#kw-camellia192
 KW-Camellia256 | http://www.w3.org/2001/04/xmldsig-more#kw-camellia256

6.1.1.  MAC Method

   When algorithms without integrity checks are used, such as AES-128-
   CBC, a keyed-MAC value MUST be placed in the <ValueMAC> element of
   the <Data> element.  In this case, the MAC algorithm type MUST be set
   in the <MACMethod> element of the <KeyContainer> element.  The MAC
   key MUST be a randomly generated key by the sender, be pre-agreed
   upon between the receiver and the sender, or be set by the
   application protocol that carries the PSKC document.  It is
   RECOMMENDED that the sender generate a random MAC key.  When the
   sender generates such a random MAC key, the MAC key material MUST be
   encrypted with the same encryption key specified in <EncryptionKey>
   element of the key container.  The encryption method and encrypted
   value MUST be set in the <EncryptionMethod> element and the
   <CipherData> element, respectively, of the <MACKey> element in the
   <MACMethod> element.  The <MACKeyReference> element of the
   <MACMethod> element MAY be used to indicate a pre-shared MAC key or a
   provisioning protocol derived MAC key.  For systems implementing
   PSKC, it is RECOMMENDED to implement the HMAC-SHA1 (with the URI of
   'http://www.w3.org/2000/09/xmldsig#hmac-sha1').  Some of the MAC
   algorithms that can optionally be implemented are:

   Algorithm      | Uniform Resource Locator (URL)
   ---------------+-----------------------------------------------------
   HMAC-SHA224    | http://www.w3.org/2001/04/xmldsig-more#hmac-sha224
   HMAC-SHA256    | http://www.w3.org/2001/04/xmldsig-more#hmac-sha256
   HMAC-SHA384    | http://www.w3.org/2001/04/xmldsig-more#hmac-sha384
   HMAC-SHA512    | http://www.w3.org/2001/04/xmldsig-more#hmac-sha512







Hoyer, et al.                Standards Track                   [Page 26]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


6.2.  Encryption Based on Passphrase-Based Keys

   Figure 7 shows an example that illustrates the encryption of the
   content of the <Secret> element using passphrase-based key derivation
   (PBKDF2) to derive the encryption key as defined in [PKCS5].  When
   using passphrase-based key derivation, the <DerivedKey> element
   defined in XML Encryption Version 1.1 [XMLENC11] MUST be used to
   specify the passphrased-based key.  A <DerivedKey> element is set as
   the child element of <EncryptionKey> element of the key container.

   The <DerivedKey> element is used to specify the key derivation
   function and related parameters.  The encryption algorithm, in this
   example, AES-128-CBC (URI
   'http://www.w3.org/2001/04/xmlenc#aes128-cbc'), MUST be set in the
   'Algorithm' attribute of <EncryptionMethod> element used inside the
   encrypted data elements.

   When PBKDF2 is used, the 'Algorithm' attribute of the <xenc11:
   KeyDerivationMethod> element MUST be set to the URI
   'http://www.rsasecurity.com/rsalabs/pkcs/schemas/pkcs-5#pbkdf2'.  The
   <xenc11:KeyDerivationMethod> element MUST include the <PBKDF2-params>
   child element to indicate the PBKDF2 parameters, such as salt and
   iteration count.

   When the encryption method uses a CBC mode that uses an explicit
   initialization vector (IV) other than a derived one, the IV MUST be
   passed by prepending it to the encrypted value.

   In the example below, the following data is used.

   Password:   qwerty

   Salt:   0x123eff3c4a72129c

   Iteration Count:  1000

   MAC Key:   0xbdaab8d648e850d25a3289364f7d7eaaf53ce581

   OTP Secret:   12345678901234567890

   The derived encryption key is "0x651e63cd57008476af1ff6422cd02e41".
   The initialization vector (IV) is
   "0xa13be8f92db69ec992d99fd1b5ca05f0".  This key is also used to
   encrypt the randomly chosen MAC key.  A different IV can be used, say
   "0xd864d39cbc0cdc8e1ee483b9164b9fa0", in the example.  The encryption
   with algorithm "AES-128-CBC" follows the specification defined in
   [XMLENC].




Hoyer, et al.                Standards Track                   [Page 27]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


  <?xml version="1.0" encoding="UTF-8"?>
  <pskc:KeyContainer
    xmlns:pskc="urn:ietf:params:xml:ns:keyprov:pskc"
    xmlns:xenc11="http://www.w3.org/2009/xmlenc11#"
    xmlns:pkcs5=
    "http://www.rsasecurity.com/rsalabs/pkcs/schemas/pkcs-5v2-0#"
    xmlns:xenc="http://www.w3.org/2001/04/xmlenc#" Version="1.0">
      <pskc:EncryptionKey>
          <xenc11:DerivedKey>
              <xenc11:KeyDerivationMethod
                Algorithm=
   "http://www.rsasecurity.com/rsalabs/pkcs/schemas/pkcs-5v2-0#pbkdf2">
                  <pkcs5:PBKDF2-params>
                      <Salt>
                          <Specified>Ej7/PEpyEpw=</Specified>
                      </Salt>
                      <IterationCount>1000</IterationCount>
                      <KeyLength>16</KeyLength>
                      <PRF/>
                  </pkcs5:PBKDF2-params>
              </xenc11:KeyDerivationMethod>
              <xenc:ReferenceList>
                  <xenc:DataReference URI="#ED"/>
              </xenc:ReferenceList>
              <xenc11:MasterKeyName>My Password 1</xenc11:MasterKeyName>
          </xenc11:DerivedKey>
      </pskc:EncryptionKey>
      <pskc:MACMethod
          Algorithm="http://www.w3.org/2000/09/xmldsig#hmac-sha1">
          <pskc:MACKey>
              <xenc:EncryptionMethod
              Algorithm="http://www.w3.org/2001/04/xmlenc#aes128-cbc"/>
              <xenc:CipherData>
                  <xenc:CipherValue>
  2GTTnLwM3I4e5IO5FkufoOEiOhNj91fhKRQBtBJYluUDsPOLTfUvoU2dStyOwYZx
                  </xenc:CipherValue>
              </xenc:CipherData>
          </pskc:MACKey>
      </pskc:MACMethod>
      <pskc:KeyPackage>
          <pskc:DeviceInfo>
              <pskc:Manufacturer>TokenVendorAcme</pskc:Manufacturer>
              <pskc:SerialNo>987654321</pskc:SerialNo>
          </pskc:DeviceInfo>
          <pskc:CryptoModuleInfo>
              <pskc:Id>CM_ID_001</pskc:Id>
          </pskc:CryptoModuleInfo>
          <pskc:Key Algorithm=



Hoyer, et al.                Standards Track                   [Page 28]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


          "urn:ietf:params:xml:ns:keyprov:pskc:hotp" Id="123456">
              <pskc:Issuer>Example-Issuer</pskc:Issuer>
              <pskc:AlgorithmParameters>
                  <pskc:ResponseFormat Length="8" Encoding="DECIMAL"/>
              </pskc:AlgorithmParameters>
              <pskc:Data>
                  <pskc:Secret>
                  <pskc:EncryptedValue Id="ED">
                      <xenc:EncryptionMethod
                          Algorithm=
  "http://www.w3.org/2001/04/xmlenc#aes128-cbc"/>
                          <xenc:CipherData>
                              <xenc:CipherValue>
        oTvo+S22nsmS2Z/RtcoF8Hfh+jzMe0RkiafpoDpnoZTjPYZu6V+A4aEn032yCr4f
                          </xenc:CipherValue>
                      </xenc:CipherData>
                      </pskc:EncryptedValue>
                      <pskc:ValueMAC>LP6xMvjtypbfT9PdkJhBZ+D6O4w=
                      </pskc:ValueMAC>
                  </pskc:Secret>
              </pskc:Data>
          </pskc:Key>
      </pskc:KeyPackage>
  </pskc:KeyContainer>

      Figure 7: Example of a PSKC Document Using Encryption Based on
                           Passphrase-Based Keys

6.3.  Encryption Based on Asymmetric Keys

   When using asymmetric keys to encrypt child elements of the <Data>
   element, information about the certificate being used MUST be stated
   in the <X509Data> element, which is a child element of the
   <EncryptionKey> element.  The encryption algorithm MUST be indicated
   in the 'Algorithm' attribute of the <EncryptionMethod> element.  In
   the example shown in Figure 8, the algorithm is set to
   'http://www.w3.org/2001/04/xmlenc#rsa_1_5'.

   <?xml version="1.0" encoding="UTF-8" ?>
   <KeyContainer
       xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
       xmlns="urn:ietf:params:xml:ns:keyprov:pskc"
       xmlns:xenc="http://www.w3.org/2001/04/xmlenc#"
       id="KC0001"
       Version="1.0">
       <EncryptionKey>
           <ds:X509Data>




Hoyer, et al.                Standards Track                   [Page 29]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   <ds:X509Certificate>MIIB5zCCAVCgAwIBAgIESZp/vDANBgkqhkiG9w0BAQUFADA4M
   Q0wCwYDVQQKEwRJRVRGMRMwEQYDVQQLEwpLZXlQcm92IFdHMRIwEAYDVQQDEwlQU0tDIF
   Rlc3QwHhcNMDkwMjE3MDkxMzMyWhcNMTEwMjE3MDkxMzMyWjA4MQ0wCwYDVQQKEwRJRVR
   GMRMwEQYDVQQLEwpLZXlQcm92IFdHMRIwEAYDVQQDEwlQU0tDIFRlc3QwgZ8wDQYJKoZI
   hvcNAQEBBQADgY0AMIGJAoGBALCWLDa2ItYJ6su80hd1gL4cggQYdyyKK17btt/aS6Q/e
   DsKjsPyFIODsxeKVV/uA3wLT4jQJM5euKJXkDajzGGOy92+ypfzTX4zDJMkh61SZwlHNJ
   xBKilAM5aW7C+BQ0RvCxvdYtzx2LTdB+X/KMEBA7uIYxLfXH2Mnub3WIh1AgMBAAEwDQY
   JKoZIhvcNAQEFBQADgYEAe875m84sYUJ8qPeZ+NG7REgTvlHTmoCdoByU0LBBLotUKuqf
   rnRuXJRMeZXaaEGmzY1kLonVjQGzjAkU4dJ+RPmiDlYuHLZS41Pg6VMwY+03lhk6I5A/w
   4rnqdkmwZX/NgXg06alnc2pBsXWhL4O7nk0S2ZrLMsQZ6HcsXgdmHo=
   </ds:X509Certificate>
           </ds:X509Data>
       </EncryptionKey>
       <KeyPackage>
           <DeviceInfo>
               <Manufacturer>TokenVendorAcme</Manufacturer>
               <SerialNo>987654321</SerialNo>
           </DeviceInfo>
           <Key
               Id="MBK000000001"
               Algorithm="urn:ietf:params:xml:ns:keyprov:pskc:hotp">
               <Issuer>Example-Issuer</Issuer>
               <AlgorithmParameters>
                   <ResponseFormat Length="6" Encoding="DECIMAL"/>
               </AlgorithmParameters>
               <Data>
                   <Secret>
                       <EncryptedValue>
                           <xenc:EncryptionMethod
                Algorithm="http://www.w3.org/2001/04/xmlenc#rsa_1_5"/>
                           <xenc:CipherData>
   <xenc:CipherValue>hJ+fvpoMPMO9BYpK2rdyQYGIxiATYHTHC7e/sPLKYo5/r1v+4
   xTYG3gJolCWuVMydJ7Ta0GaiBPHcWa8ctCVYmHKfSz5fdeV5nqbZApe6dofTqhRwZK6
   Yx4ufevi91cjN2vBpSxYafvN3c3+xIgk0EnTV4iVPRCR0rBwyfFrPc4=
   </xenc:CipherValue>
                           </xenc:CipherData>
                       </EncryptedValue>
                   </Secret>
                   <Counter>
                       <PlainValue>0</PlainValue>
                   </Counter>
               </Data>
           </Key>
       </KeyPackage>
   </KeyContainer>

      Figure 8: Example of a PSKC Document Using Encryption Based on
                              Asymmetric Keys



Hoyer, et al.                Standards Track                   [Page 30]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   For systems implementing PSKC, it is RECOMMENDED to implement the
   RSA-1.5 algorithm, identified by the URI
   'http://www.w3.org/2001/04/xmlenc#rsa-1_5'.

   Some of the asymmetric encryption algorithms that can optionally be
   implemented are:

   Algorithm         | Uniform Resource Locator (URL)
   ------------------+-------------------------------------------------
   RSA-OAEP-MGF1P    | http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p

6.4.  Padding of Encrypted Values for Non-Padded Encryption Algorithms

   Padding of encrypted values (for example, the key secret value) is
   required when key protection algorithms are used that do not support
   embedded padding and the value to be encrypted is not a multiple of
   the encryption algorithm cipher block length.

   For example, when transmitting an HOTP key (20 bytes long) protected
   with the AES algorithm in CBC mode (8-byte block cipher), padding is
   required since its length is not a multiple of the 8-byte block
   length.

   In these cases, for systems implementing PSKC, it is RECOMMENDED to
   pad the value before encryption using PKCS #5 padding as described in
   [PKCS5].

7.  Digital Signature

   PSKC allows a digital signature to be added to the XML document, as a
   child element of the <KeyContainer> element.  The description of the
   XML digital signature can be found in [XMLDSIG].

   <?xml version="1.0" encoding="UTF-8"?>
   <KeyContainer
       xmlns="urn:ietf:params:xml:ns:keyprov:pskc"
       xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
       xmlns:xenc="http://www.w3.org/2001/04/xmlenc#"
       Version="1.0">
       <KeyPackage>
           <DeviceInfo>
               <Manufacturer>TokenVendorAcme</Manufacturer>
               <SerialNo>0755225266</SerialNo>
           </DeviceInfo>
           <Key Id="123"
           Algorithm="urn:ietf:params:xml:ns:keyprov:pskc:hotp">
               <Issuer>Example-Issuer</Issuer>
               <AlgorithmParameters>



Hoyer, et al.                Standards Track                   [Page 31]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


                   <ResponseFormat Length="6" Encoding="DECIMAL"/>
               </AlgorithmParameters>
               <Data>
                   <Secret>
                       <PlainValue>
                           MTIzNDU2Nzg5MDEyMzQ1Njc4OTA=
                       </PlainValue>
                   </Secret>
                   <Counter>
                       <PlainValue>0</PlainValue>
                   </Counter>
               </Data>
           </Key>
       </KeyPackage>
       <Signature>
           <ds:SignedInfo>
               <ds:CanonicalizationMethod
                Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
               <ds:SignatureMethod
                Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1"/>
               <ds:Reference URI="#Device">
                   <ds:DigestMethod
                Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>
                   <ds:DigestValue>
                       j6lwx3rvEPO0vKtMup4NbeVu8nk=
                   </ds:DigestValue>
               </ds:Reference>
           </ds:SignedInfo>
           <ds:SignatureValue>
               j6lwx3rvEPO0vKtMup4NbeVu8nk=
           </ds:SignatureValue>
           <ds:KeyInfo>
               <ds:X509Data>
                   <ds:X509IssuerSerial>
                       <ds:X509IssuerName>
                           CN=Example.com,C=US
                       </ds:X509IssuerName>
                       <ds:X509SerialNumber>
                           12345678
                       </ds:X509SerialNumber>
                   </ds:X509IssuerSerial>
               </ds:X509Data>
           </ds:KeyInfo>
       </Signature>
   </KeyContainer>

                    Figure 9: Digital Signature Example




Hoyer, et al.                Standards Track                   [Page 32]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


8.  Bulk Provisioning

   The functionality of bulk provisioning can be accomplished by
   repeating the <KeyPackage> element multiple times within the
   <KeyContainer> element, indicating that multiple keys are provided to
   different devices or cryptographic modules.  The <EncryptionKey>
   element then applies to all <KeyPackage> elements.  When provisioning
   multiple keys to the same device, the <KeyPackage> element is
   repeated, but the enclosed <DeviceInfo> element will contain the same
   sub-elements that uniquely identify the single device (for example,
   the keys for the device identified by SerialNo='9999999' in the
   example below).

   Figure 10 shows an example utilizing these capabilities.

   <?xml version="1.0" encoding="UTF-8"?>
   <KeyContainer Version="1.0"
       xmlns="urn:ietf:params:xml:ns:keyprov:pskc">
       <KeyPackage>
           <DeviceInfo>
               <Manufacturer>TokenVendorAcme</Manufacturer>
               <SerialNo>654321</SerialNo>
           </DeviceInfo>
           <Key Id="1"
           Algorithm="urn:ietf:params:xml:ns:keyprov:pskc:hotp">
               <Issuer>Issuer</Issuer>
               <AlgorithmParameters>
                   <ResponseFormat Length="8" Encoding="DECIMAL"/>
               </AlgorithmParameters>
               <Data>
                   <Secret>
                       <PlainValue>
                           MTIzNDU2Nzg5MDEyMzQ1Njc4OTA=
                       </PlainValue>
                   </Secret>
                   <Counter>
                       <PlainValue>0</PlainValue>
                   </Counter>
               </Data>
               <Policy>
                   <StartDate>2006-05-01T00:00:00Z</StartDate>
                   <ExpiryDate>2006-05-31T00:00:00Z</ExpiryDate>
               </Policy>
           </Key>
       </KeyPackage>






Hoyer, et al.                Standards Track                   [Page 33]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


       <KeyPackage>
           <DeviceInfo>
               <Manufacturer>TokenVendorAcme</Manufacturer>
               <SerialNo>123456</SerialNo>
           </DeviceInfo>
           <Key Id="2"
           Algorithm="urn:ietf:params:xml:ns:keyprov:pskc:hotp">
               <Issuer>Issuer</Issuer>
               <AlgorithmParameters>
                   <ResponseFormat Length="8" Encoding="DECIMAL"/>
               </AlgorithmParameters>
               <Data>
                   <Secret>
                       <PlainValue>
                           MTIzNDU2Nzg5MDEyMzQ1Njc4OTA=
                       </PlainValue>
                   </Secret>
                   <Counter>
                       <PlainValue>0</PlainValue>
                   </Counter>
               </Data>
               <Policy>
                   <StartDate>2006-05-01T00:00:00Z</StartDate>
                   <ExpiryDate>2006-05-31T00:00:00Z</ExpiryDate>
               </Policy>
           </Key>
       </KeyPackage>
       <KeyPackage>
           <DeviceInfo>
               <Manufacturer>TokenVendorAcme</Manufacturer>
               <SerialNo>9999999</SerialNo>
           </DeviceInfo>
           <Key Id="3"
           Algorithm="urn:ietf:params:xml:ns:keyprov:pskc:hotp">
               <Issuer>Issuer</Issuer>
               <AlgorithmParameters>
                   <ResponseFormat Length="8" Encoding="DECIMAL"/>
               </AlgorithmParameters>
               <Data>
                   <Secret>
                       <PlainValue>
                           MTIzNDU2Nzg5MDEyMzQ1Njc4OTA=
                       </PlainValue>
                   </Secret>
                   <Counter>
                       <PlainValue>0</PlainValue>
                   </Counter>
               </Data>



Hoyer, et al.                Standards Track                   [Page 34]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


               <Policy>
                   <StartDate>2006-03-01T00:00:00Z</StartDate>
                   <ExpiryDate>2006-03-31T00:00:00Z</ExpiryDate>
               </Policy>
           </Key>
       </KeyPackage>
       <KeyPackage>
           <DeviceInfo>
               <Manufacturer>TokenVendorAcme</Manufacturer>
               <SerialNo>9999999</SerialNo>
           </DeviceInfo>
           <Key Id="4"
           Algorithm="urn:ietf:params:xml:ns:keyprov:pskc:hotp">
               <Issuer>Issuer</Issuer>
               <AlgorithmParameters>
                   <ResponseFormat Length="8" Encoding="DECIMAL"/>
               </AlgorithmParameters>
               <Data>
                   <Secret>
                       <PlainValue>
                           MTIzNDU2Nzg5MDEyMzQ1Njc4OTA=
                       </PlainValue>
                   </Secret>
                   <Counter>
                       <PlainValue>0</PlainValue>
                   </Counter>
               </Data>
               <Policy>
                   <StartDate>2006-04-01T00:00:00Z</StartDate>
                   <ExpiryDate>2006-04-30T00:00:00Z</ExpiryDate>
               </Policy>
           </Key>
       </KeyPackage>
   </KeyContainer>

                   Figure 10: Bulk Provisioning Example

9.  Extensibility

   This section lists a few common extension points provided by PSKC:

   New PSKC Version:  Whenever it is necessary to define a new version
      of this document, a new version number has to be allocated to
      refer to the new specification.  The version number is carried
      inside the 'Version' attribute, as described in Section 4, the
      numbering scheme MUST follow Section 1.2, and rules for
      extensibility are defined in Section 12.




Hoyer, et al.                Standards Track                   [Page 35]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   New XML Elements:  The usage of the XML schema and the available
      extension points allows new XML elements to be added.  Depending
      on the type of XML element, different ways for extensibility are
      offered.  In some places, the <Extensions> element can be used and
      elsewhere the "<xs:any namespace="##other" processContents="lax"
      minOccurs="0" maxOccurs="unbounded"/>" XML extension point is
      utilized.

   New XML Attributes:  The XML schema allows new XML attributes to be
      added where XML extension points have been defined (see "<xs:
      anyAttribute namespace="##other"/>" in Section 11).

   New PSKC Algorithm Profiles:  This document defines two PSKC
      algorithm profiles, see Section 10.  The following informational
      document describes additional profiles [PSKC-ALGORITHM-PROFILES].
      Further PSKC algorithm profiles can be registered as described in
      Section 12.4.

   Algorithm URIs:  Section 6 defines how keys and related data can be
      protected.  A number of algorithms can be used.  New algorithms
      can be used by pointing to a new algorithm URI.

   Policy:  Section 5 defines policies that can be attached to a key and
      keying-related data.  The <Policy> element is one such item that
      allows implementers to restrict the use of the key to certain
      functions, such as "OTP usage only".  Further values may be
      registered as described in Section 12.

10.  PSKC Algorithm Profile

10.1.  HOTP

   Common Name:  HOTP

   Class:  OTP

   URI:  urn:ietf:params:xml:ns:keyprov:pskc:hotp

   Algorithm Definition:  [HOTP]

   Identifier Definition:  (this RFC)

   Registrant Contact:  IESG

   Deprecated:  FALSE






Hoyer, et al.                Standards Track                   [Page 36]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   Profiling:

         The <KeyPackage> element MUST be present and the
         <ResponseFormat> element, which is a child element of the
         <AlgorithmParameters> element, MUST be used to indicate the OTP
         length and the value format.

         The <Counter> element (see Section 4.1) MUST be provided as
         metadata for the key.

         The following additional constraints apply:

         +  The value of the <Secret> element MUST contain key material
            with a length of at least 16 octets (128 bits), if it is
            present.

         +  The <ResponseFormat> element MUST have the 'Format'
            attribute set to "DECIMAL", and the 'Length' attribute MUST
            indicate a length value between 6 and 9 (inclusive).

         +  The <PINPolicy> element MAY be present, but the
            'PINUsageMode' attribute cannot be set to "Algorithmic".

         An example can be found in Figure 3.

10.2.  PIN

   Common Name:  PIN

   Class:  Symmetric static credential comparison

   URI:  urn:ietf:params:xml:ns:keyprov:pskc:pin

   Algorithm Definition:  (this RFC) Section 5.1

   Identifier Definition  (this RFC)

   Registrant Contact:  IESG

   Deprecated:  FALSE

   Profiling:

         The <Usage> element MAY be present, but no attribute of the
         <Usage> element is required.  The <ResponseFormat> element MAY
         be used to indicate the PIN value format.





Hoyer, et al.                Standards Track                   [Page 37]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


         The <Secret> element (see Section 4.1) MUST be provided.

         See the example in Figure 5

11.  XML Schema

   This section defines the XML schema for PSKC.

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
     xmlns:pskc="urn:ietf:params:xml:ns:keyprov:pskc"
     xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
     xmlns:xenc="http://www.w3.org/2001/04/xmlenc#"
     targetNamespace="urn:ietf:params:xml:ns:keyprov:pskc"
     elementFormDefault="qualified"
     attributeFormDefault="unqualified">
     <xs:import namespace="http://www.w3.org/2000/09/xmldsig#"
          schemaLocation=
"http://www.w3.org/TR/2002/REC-xmldsig-core-20020212/
          xmldsig-core-schema.xsd"/>
     <xs:import namespace="http://www.w3.org/2001/04/xmlenc#"
          schemaLocation=
"http://www.w3.org/TR/2002/REC-xmlenc-core-20021210/xenc-schema.xsd"/>
     <xs:import namespace="http://www.w3.org/XML/1998/namespace"/>
     <xs:complexType name="KeyContainerType">
          <xs:sequence>
               <xs:element name="EncryptionKey"
                    type="ds:KeyInfoType" minOccurs="0"/>
               <xs:element name="MACMethod"
                    type="pskc:MACMethodType" minOccurs="0"/>
               <xs:element name="KeyPackage"
                    type="pskc:KeyPackageType" maxOccurs="unbounded"/>
               <xs:element name="Signature"
                    type="ds:SignatureType" minOccurs="0"/>
               <xs:element name="Extensions"
                    type="pskc:ExtensionsType"
                    minOccurs="0" maxOccurs="unbounded"/>
          </xs:sequence>
          <xs:attribute name="Version"
               type="pskc:VersionType" use="required"/>
          <xs:attribute name="Id"
               type="xs:ID" use="optional"/>
     </xs:complexType>
     <xs:simpleType name="VersionType" final="restriction">
          <xs:restriction base="xs:string">
               <xs:pattern value="\d{1,2}\.\d{1,3}"/>
          </xs:restriction>




Hoyer, et al.                Standards Track                   [Page 38]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


     </xs:simpleType>
     <xs:complexType name="KeyType">
          <xs:sequence>
               <xs:element name="Issuer"
                    type="xs:string" minOccurs="0"/>
               <xs:element name="AlgorithmParameters"
                    type="pskc:AlgorithmParametersType"
                    minOccurs="0"/>
               <xs:element name="KeyProfileId"
                    type="xs:string" minOccurs="0"/>
               <xs:element name="KeyReference"
                    type="xs:string" minOccurs="0"/>
               <xs:element name="FriendlyName"
                    type="xs:string" minOccurs="0"/>
               <xs:element name="Data"
                    type="pskc:KeyDataType" minOccurs="0"/>
               <xs:element name="UserId"
                    type="xs:string" minOccurs="0"/>
               <xs:element name="Policy"
                    type="pskc:PolicyType" minOccurs="0"/>
               <xs:element name="Extensions"
                    type="pskc:ExtensionsType" minOccurs="0"
                    maxOccurs="unbounded"/>
          </xs:sequence>
          <xs:attribute name="Id"
               type="xs:string" use="required"/>
          <xs:attribute name="Algorithm"
               type="pskc:KeyAlgorithmType" use="optional"/>
     </xs:complexType>
     <xs:complexType name="PolicyType">
          <xs:sequence>
               <xs:element name="StartDate"
                    type="xs:dateTime" minOccurs="0"/>
               <xs:element name="ExpiryDate"
                    type="xs:dateTime" minOccurs="0"/>
               <xs:element name="PINPolicy"
                    type="pskc:PINPolicyType" minOccurs="0"/>
               <xs:element name="KeyUsage"
                    type="pskc:KeyUsageType"
                    minOccurs="0" maxOccurs="unbounded"/>
               <xs:element name="NumberOfTransactions"
                    type="xs:nonNegativeInteger" minOccurs="0"/>
               <xs:any namespace="##other"
                    minOccurs="0" maxOccurs="unbounded"/>
          </xs:sequence>
     </xs:complexType>
     <xs:complexType name="KeyDataType">
          <xs:sequence>



Hoyer, et al.                Standards Track                   [Page 39]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


               <xs:element name="Secret"
                    type="pskc:binaryDataType" minOccurs="0"/>
               <xs:element name="Counter"
                    type="pskc:longDataType" minOccurs="0"/>
               <xs:element name="Time"
                    type="pskc:intDataType" minOccurs="0"/>
               <xs:element name="TimeInterval"
                    type="pskc:intDataType" minOccurs="0"/>
               <xs:element name="TimeDrift"
                    type="pskc:intDataType" minOccurs="0"/>
               <xs:any namespace="##other"
                    processContents="lax"
                    minOccurs="0" maxOccurs="unbounded"/>
          </xs:sequence>
     </xs:complexType>
     <xs:complexType name="binaryDataType">
          <xs:sequence>
               <xs:choice>
                    <xs:element name="PlainValue"
                         type="xs:base64Binary"/>
                    <xs:element name="EncryptedValue"
                         type="xenc:EncryptedDataType"/>
               </xs:choice>
               <xs:element name="ValueMAC"
                    type="xs:base64Binary" minOccurs="0"/>
          </xs:sequence>
     </xs:complexType>
     <xs:complexType name="intDataType">
          <xs:sequence>
               <xs:choice>
                    <xs:element name="PlainValue" type="xs:int"/>
                    <xs:element name="EncryptedValue"
                         type="xenc:EncryptedDataType"/>
               </xs:choice>
               <xs:element name="ValueMAC"
                    type="xs:base64Binary" minOccurs="0"/>
          </xs:sequence>
     </xs:complexType>
     <xs:complexType name="stringDataType">
          <xs:sequence>
               <xs:choice>
                    <xs:element name="PlainValue" type="xs:string"/>
                    <xs:element name="EncryptedValue"
                         type="xenc:EncryptedDataType"/>
               </xs:choice>
               <xs:element name="ValueMAC"
                    type="xs:base64Binary" minOccurs="0"/>
          </xs:sequence>



Hoyer, et al.                Standards Track                   [Page 40]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


     </xs:complexType>
     <xs:complexType name="longDataType">
          <xs:sequence>
               <xs:choice>
                    <xs:element name="PlainValue" type="xs:long"/>
                    <xs:element name="EncryptedValue"
                         type="xenc:EncryptedDataType"/>
               </xs:choice>
               <xs:element name="ValueMAC"
                    type="xs:base64Binary" minOccurs="0"/>
          </xs:sequence>
     </xs:complexType>
     <xs:complexType name="PINPolicyType">
          <xs:attribute name="PINKeyId"
               type="xs:string" use="optional"/>
          <xs:attribute name="PINUsageMode"
               type="pskc:PINUsageModeType"/>
          <xs:attribute name="MaxFailedAttempts"
               type="xs:unsignedInt" use="optional"/>
          <xs:attribute name="MinLength"
               type="xs:unsignedInt" use="optional"/>
          <xs:attribute name="MaxLength"
               type="xs:unsignedInt" use="optional"/>
          <xs:attribute name="PINEncoding"
               type="pskc:ValueFormatType" use="optional"/>
          <xs:anyAttribute namespace="##other"/>
     </xs:complexType>
     <xs:simpleType name="PINUsageModeType">
          <xs:restriction base="xs:string">
               <xs:enumeration value="Local"/>
               <xs:enumeration value="Prepend"/>
               <xs:enumeration value="Append"/>
               <xs:enumeration value="Algorithmic"/>
          </xs:restriction>
     </xs:simpleType>
     <xs:simpleType name="KeyUsageType">
          <xs:restriction base="xs:string">
               <xs:enumeration value="OTP"/>
               <xs:enumeration value="CR"/>
               <xs:enumeration value="Encrypt"/>
               <xs:enumeration value="Integrity"/>
               <xs:enumeration value="Verify"/>
               <xs:enumeration value="Unlock"/>
               <xs:enumeration value="Decrypt"/>
               <xs:enumeration value="KeyWrap"/>
               <xs:enumeration value="Unwrap"/>
               <xs:enumeration value="Derive"/>
               <xs:enumeration value="Generate"/>



Hoyer, et al.                Standards Track                   [Page 41]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


          </xs:restriction>
     </xs:simpleType>
     <xs:complexType name="DeviceInfoType">
          <xs:sequence>
               <xs:element name="Manufacturer"
                    type="xs:string" minOccurs="0"/>
               <xs:element name="SerialNo"
                    type="xs:string" minOccurs="0"/>
               <xs:element name="Model"
                    type="xs:string" minOccurs="0"/>
               <xs:element name="IssueNo"
                    type="xs:string" minOccurs="0"/>
               <xs:element name="DeviceBinding"
                    type="xs:string" minOccurs="0"/>
               <xs:element name="StartDate"
                    type="xs:dateTime" minOccurs="0"/>
               <xs:element name="ExpiryDate"
                    type="xs:dateTime" minOccurs="0"/>
               <xs:element name="UserId"
                    type="xs:string" minOccurs="0"/>
               <xs:element name="Extensions"
                    type="pskc:ExtensionsType" minOccurs="0"
                    maxOccurs="unbounded"/>
          </xs:sequence>
     </xs:complexType>
     <xs:complexType name="CryptoModuleInfoType">
          <xs:sequence>
               <xs:element name="Id" type="xs:string"/>
               <xs:element name="Extensions"
                    type="pskc:ExtensionsType" minOccurs="0"
                    maxOccurs="unbounded"/>
          </xs:sequence>
     </xs:complexType>
     <xs:complexType name="KeyPackageType">
          <xs:sequence>
               <xs:element name="DeviceInfo"
                    type="pskc:DeviceInfoType" minOccurs="0"/>
               <xs:element name="CryptoModuleInfo"
                    type="pskc:CryptoModuleInfoType" minOccurs="0"/>
               <xs:element name="Key"
                    type="pskc:KeyType" minOccurs="0"/>
               <xs:element name="Extensions"
                    type="pskc:ExtensionsType" minOccurs="0"
                    maxOccurs="unbounded"/>
          </xs:sequence>
     </xs:complexType>
     <xs:complexType name="AlgorithmParametersType">
          <xs:choice>



Hoyer, et al.                Standards Track                   [Page 42]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


               <xs:element name="Suite" type="xs:string" minOccurs="0"/>
               <xs:element name="ChallengeFormat" minOccurs="0">
                    <xs:complexType>
                         <xs:attribute name="Encoding"
                              type="pskc:ValueFormatType"
                                                      use="required"/>
                         <xs:attribute name="Min"
                              type="xs:unsignedInt" use="required"/>
                         <xs:attribute name="Max"
                              type="xs:unsignedInt" use="required"/>
                         <xs:attribute name="CheckDigits"
                              type="xs:boolean" default="false"/>
                    </xs:complexType>
               </xs:element>
               <xs:element name="ResponseFormat" minOccurs="0">
                    <xs:complexType>
                         <xs:attribute name="Encoding"
                              type="pskc:ValueFormatType"
                                                      use="required"/>
                         <xs:attribute name="Length"
                              type="xs:unsignedInt" use="required"/>
                         <xs:attribute name="CheckDigits"
                              type="xs:boolean" default="false"/>
                    </xs:complexType>
               </xs:element>
               <xs:element name="Extensions"
                    type="pskc:ExtensionsType" minOccurs="0"
                    maxOccurs="unbounded"/>
          </xs:choice>
     </xs:complexType>
     <xs:complexType name="ExtensionsType">
          <xs:sequence>
               <xs:any namespace="##other"
                    processContents="lax" maxOccurs="unbounded"/>
          </xs:sequence>
          <xs:attribute name="definition"
               type="xs:anyURI" use="optional"/>
     </xs:complexType>
     <xs:simpleType name="KeyAlgorithmType">
          <xs:restriction base="xs:anyURI"/>
     </xs:simpleType>
     <xs:simpleType name="ValueFormatType">
          <xs:restriction base="xs:string">
               <xs:enumeration value="DECIMAL"/>
               <xs:enumeration value="HEXADECIMAL"/>
               <xs:enumeration value="ALPHANUMERIC"/>
               <xs:enumeration value="BASE64"/>
               <xs:enumeration value="BINARY"/>



Hoyer, et al.                Standards Track                   [Page 43]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


          </xs:restriction>
     </xs:simpleType>
     <xs:complexType name="MACMethodType">
           <xs:sequence>
                  <xs:choice>
                        <xs:element name="MACKey"
              type="xenc:EncryptedDataType" minOccurs="0"/>
                        <xs:element name="MACKeyReference"
                                type="xs:string" minOccurs="0"/>
                        </xs:choice>
                        <xs:any namespace="##other"
           processContents="lax" minOccurs="0" maxOccurs="unbounded"/>
       </xs:sequence>
       <xs:attribute name="Algorithm" type="xs:anyURI" use="required"/>
        </xs:complexType>
     <xs:element name="KeyContainer"
          type="pskc:KeyContainerType"/>
</xs:schema>

12.  IANA Considerations

12.1.  Content-Type Registration for 'application/pskc+xml'

   This specification contains the registration of a new media type
   according to the procedures of RFC 4288 [RFC4288] and guidelines in
   RFC 3023 [RFC3023].

   MIME media type name:  application

   MIME subtype name:  pskc+xml

   Required parameters:  There is no required parameter.

   Optional parameters:  charset

      Indicates the character encoding of enclosed XML.

   Encoding considerations:  Uses XML, which can employ 8-bit
      characters, depending on the character encoding used.  See RFC
      3023 [RFC3023], Section 3.2.

   Security considerations:  Please refer to Section 13 of RFC 6030.

   Interoperability considerations:  None







Hoyer, et al.                Standards Track                   [Page 44]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   Published specification:  RFC 6030.

   Applications which use this media type:  This media type is being
      used as a symmetric key container format for transport and
      provisioning of symmetric keys (One-Time Password (OTP) shared
      secrets or symmetric cryptographic keys) to different types of
      strong authentication devices.  As such, it is used for key
      provisioning systems.

   Additional information:

      Magic Number:  None

      File Extension:  .pskcxml

      Macintosh file type code:  'TEXT'

   Personal and email address to contact for further information:
      Philip Hoyer, Philip.Hoyer@actividentity.com

   Intended usage:  LIMITED USE

   Restrictions on usage:  None

   Author:  This specification is a work item of the IETF KEYPROV
      working group, with mailing list address <keyprov@ietf.org>.

   Change controller:  The IESG <iesg@ietf.org>

12.2.  XML Schema Registration

   This section registers an XML schema as per the guidelines in
   [RFC3688].

   URI:  urn:ietf:params:xml:schema:keyprov:pskc

   Registrant Contact:  IETF KEYPROV Working Group, Philip Hoyer
      (Philip.Hoyer@actividentity.com).

   XML Schema:  The XML schema to be registered is contained in
      Section 11.  Its first line is

   <?xml version="1.0" encoding="UTF-8"?>

   and its last line is

   </xs:schema>




Hoyer, et al.                Standards Track                   [Page 45]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


12.3.  URN Sub-Namespace Registration

   This section registers a new XML namespace,
   "urn:ietf:params:xml:ns:keyprov:pskc", per the guidelines in
   [RFC3688].

   URI:  urn:ietf:params:xml:ns:keyprov:pskc

   Registrant Contact:  IETF KEYPROV Working Group, Philip Hoyer
      (Philip.Hoyer@actividentity.com).

   XML:

   BEGIN
   <?xml version="1.0"?>
   <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
     "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
   <html xmlns="http://www.w3.org/1999/xhtml">
   <head>
     <meta http-equiv="content-type"
           content="text/html;charset=iso-8859-1"/>
     <title>PSKC Namespace</title>
   </head>
   <body>
     <h1>Namespace for PSKC</h1>
     <h2>urn:ietf:params:xml:ns:keyprov:pskc</h2>
   <p>See <a href="http://www.rfc-editor.org/rfc/rfc6030.txt">
    RFC 6030</a>.</p>
   </body>
   </html>
   END

12.4.  PSKC Algorithm Profile Registry

   IANA has created a registry for PSKC algorithm profiles in accordance
   with the principles set out in RFC 5226 [RFC5226].

   As part of this registry, IANA maintains the following information:

   Common Name:  The name by which the PSKC algorithm profile is
      generally referred.

   Class:  The type of PSKC algorithm profile registry entry being
      created, such as encryption, Message Authentication Code (MAC),
      One-Time Password (OTP), Digest.






Hoyer, et al.                Standards Track                   [Page 46]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   URI:  The URI to be used to identify the profile.

   Identifier Definition:  IANA will add a pointer to the specification
      containing information about the PSKC algorithm profile
      registration.

   Algorithm Definition:  A reference to the stable document in which
      the algorithm being used with the PSKC is defined.

   Registrant Contact:  Contact information about the party submitting
      the registration request.

   Deprecated:  TRUE if this entry has been deprecated based on expert
      approval and SHOULD not be used in any new implementations.
      Otherwise, FALSE.

   PSKC Profiling:  Information about PSKC XML elements and attributes
      being used (or not) with this specific profile of PSKC.

   PSKC algorithm profile identifier registrations are to be subject to
   Specification Required as per RFC 5226 [RFC5226].  Updates can be
   provided based on expert approval only.  Based on expert approval, it
   is possible to mark entries as "deprecated".  A designated expert
   will be appointed by the IESG.

   IANA has added two initial values to the registry based on the
   algorithm profiles described in Section 10.

12.5.  PSKC Version Registry

   IANA has created a registry for PSKC version numbers.  The registry
   has the following structure:

     PSKC Version              | Specification
   +---------------------------+----------------
   | 1.0                       | RFC 6030

   Standards action is required to define new versions of PSKC.  It is
   not envisioned to deprecate, delete, or modify existing PSKC
   versions.

12.6.  Key Usage Registry

   IANA has created a registry for key usage.  A description of the
   <KeyUsage> element can be found in Section 5.






Hoyer, et al.                Standards Track                   [Page 47]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   As part of this registry IANA will maintain the following
   information:

    Key Usage:  The identifier of the Key Usage.

   Specification:  IANA will add a pointer to the specification
      containing information about the semantics of a new Key Usage
      registration.

   Deprecated:  TRUE if this entry has been deprecated based on expert
      approval and SHOULD not be used in any new implementations.
      Otherwise, FALSE.

   IANA has added these initial values to the registry:

     Key Usage     | Specification                | Deprecated
   +---------------+------------------------------+-----------
   | OTP           | [Section 5 of this document] | FALSE
   | CR            | [Section 5 of this document] | FALSE
   | Encrypt       | [Section 5 of this document] | FALSE
   | Integrity     | [Section 5 of this document] | FALSE
   | Verify        | [Section 5 of this document] | FALSE
   | Unlock        | [Section 5 of this document] | FALSE
   | Decrypt       | [Section 5 of this document] | FALSE
   | KeyWrap       | [Section 5 of this document] | FALSE
   | Unwrap        | [Section 5 of this document] | FALSE
   | Derive        | [Section 5 of this document] | FALSE
   | Generate      | [Section 5 of this document] | FALSE
   +---------------+------------------------------+-----------

   Key Usage Registry registrations are to be subject to Specification
   Required as per RFC 5226 [RFC5226].  Expert Review is required to
   define new Key Usage values.  Updates can be provided based on expert
   approval only.  Based on expert approval, it is possible to mark
   entries as "deprecated".  A designated expert will be appointed by
   the IESG.

13.  Security Considerations

   The portable symmetric key container (PSKC) carries sensitive
   information (e.g., cryptographic keys) and may be transported across
   the boundaries of one secure perimeter to another.  For example, a
   container residing within the secure perimeter of a back-end
   provisioning server in a secure room may be transported across the
   Internet to an end-user device attached to a personal computer.  This
   means that special care MUST be taken to ensure the confidentiality,
   integrity, and authenticity of the information contained within.




Hoyer, et al.                Standards Track                   [Page 48]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


13.1.  PSKC Confidentiality

   By design, the container allows two main approaches to guaranteeing
   the confidentiality of the information it contains while transported.

   First, the container key data payload may be encrypted.

   In this case, no transport layer security is required.  However,
   standard security best practices apply when selecting the strength of
   the cryptographic algorithm for key data payload encryption.  A
   symmetric cryptographic cipher SHOULD be used -- the longer the
   cryptographic key, the stronger the protection.  Please see
   Section 6.1 for recommendations of key data payload protection using
   symmetric cryptographic ciphers.  In cases where the exchange of key
   encryption keys between the sender and the receiver is not possible,
   asymmetric encryption of the key data payload may be employed, see
   Section 6.3.  Similar to symmetric key cryptography, the stronger the
   asymmetric key, the more secure the protection.

   If the key data payload is encrypted with a method that uses one of
   the password-based encryption methods (PBE methods) detailed in
   Section 6.2, the key data payload may be subjected to password
   dictionary attacks to break the encryption password and recover the
   information.  Standard security best practices for selection of
   strong encryption passwords apply.

   Additionally, it is strongly RECOMMENDED that practical
   implementations use PBESalt and PBEIterationCount when PBE encryption
   is used.  A different PBESalt value per PSKC SHOULD be used for best
   protection.

   The second approach to protecting the confidentiality of the key data
   is based on using lower-layer security mechanisms (e.g., [TLS],
   [IPsec]).  The secure connection established between the source
   secure perimeter (the provisioning server from the example above) and
   the target perimeter (the device attached to the end-user computer)
   utilizes encryption to protect the messages that travel across that
   connection.  No key data payload encryption is required in this mode.
   Secure connections that encrypt and digest each message provide an
   extra measure of security.

   Because of the fact that the plaintext PSKC is protected only by the
   transport layer security, practical implementation MUST ensure
   protection against man-in-the-middle attacks.  Authenticating the
   secure channel endpoints is critically important for eliminating
   intruders that may compromise the confidentiality of the PSKC.





Hoyer, et al.                Standards Track                   [Page 49]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


13.2.  PSKC Integrity

   The PSKC provides means to guarantee the integrity of the information
   it contains through the use of digital signatures.  It is RECOMMENDED
   that for best security practices, the digital signature of the
   container encompasses the entire PSKC.  This provides assurances for
   the integrity of all attributes.  It also allows verification of the
   integrity of a given PSKC even after the container is delivered
   through the communication channel to the target perimeter and channel
   message integrity check is no longer possible.

13.3.  PSKC Authenticity

   The digital signature of the PSKC is the primary way of showing its
   authenticity.  The recipient of the container SHOULD use the public
   key associated with the signature to assert the authenticity of the
   sender by tracing it back to a pre-loaded public key or certificate.
   Note that the digital signature of the PSKC can be checked even after
   the container has been delivered through the secure channel of
   communication.

   Authenticity guarantee may be provided by [TLS] or [IPsec].  However,
   no authenticity verification is possible once the container is
   delivered at the recipient end.  Since the TLS endpoints could differ
   from the key provisioning endpoints, this solution is weaker than the
   previous solution that relies on a digital signature of the PSKC.

14.  Contributors

   We would like Hannes Tschofenig for his text contributions to this
   document.

15.  Acknowledgements

   The authors of this document would like to thank the following people
   for their feedback: Apostol Vassilev, Shuh Chang, Jon Martinson,
   Siddhart Bajaj, Stu Vaeth, Kevin Lewis, Philip Hallam-Baker, Andrea
   Doherty, Magnus Nystrom, Tim Moses, Anders Rundgren, Sean Turner, and
   especially Robert Philpott.

   We would like to thank Sean Turner for his review in January 2009.
   We would also like to thank Anders Rundgren for triggering the
   discussion regarding to the selection of encryption algorithms
   (KW-AES-128 vs. AES-128-CBC) and his input on the keyed message
   digest computation.






Hoyer, et al.                Standards Track                   [Page 50]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   This work is based on earlier work by the members of OATH (Initiative
   for Open AuTHentication), see [OATH], to specify a format that can be
   freely distributed to the technical community.

16.  References

16.1.  Normative References

   [FIPS197]  National Institute of Standards, "FIPS Pub 197: Advanced
              Encryption Standard (AES)", November 2001.

   [HOTP]     M'Raihi, D., Bellare, M., Hoornaert, F., Naccache, D., and
              O. Ranen, "HOTP: An HMAC-Based One-Time Password
              Algorithm", RFC 4226, December 2005.

   [IANAPENREG]
              IANA, "Private Enterprise Numbers", <http://www.iana.org>.

   [ISOIEC7812]
              ISO, "ISO/IEC 7812-1:2006 Identification cards --
              Identification of issuers -- Part 1: Numbering system",
              October 2006, <http://www.iso.org/iso/iso_catalogue/
              catalogue_tc/catalogue_detail.htm?csnumber=39698>.

   [OATHMAN]  OATH, "List of OATH Manufacturer Prefixes (omp)",
              April 2009,
              <http://www.openauthentication.org/oath-id/prefixes/>.

   [PKCS5]    RSA Laboratories, "PKCS #5: Password-Based Cryptography
              Standard", Version 2.0, March 1999,
              <http://www.rsasecurity.com/rsalabs/pkcs/>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3023]  Murata, M., St. Laurent, S., and D. Kohn, "XML Media
              Types", RFC 3023, January 2001.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              January 2004.

   [RFC4288]  Freed, N. and J. Klensin, "Media Type Specifications and
              Registration Procedures", BCP 13, RFC 4288, December 2005.

   [RFC4514]  Zeilenga, K., "Lightweight Directory Access Protocol
              (LDAP): String Representation of Distinguished Names",
              RFC 4514, June 2006.




Hoyer, et al.                Standards Track                   [Page 51]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, October 2006.

   [RFC5646]  Phillips, A. and M. Davis, "Tags for Identifying
              Languages", BCP 47, RFC 5646, September 2009.

   [RFC5649]  Housley, R. and M. Dworkin, "Advanced Encryption Standard
              (AES) Key Wrap with Padding Algorithm", RFC 5649,
              September 2009.

   [SP800-67]
              National Institute of Standards, "NIST Special Publication
              800-67 Version 1.1: Recommendation for the Triple Data
              Encryption Algorithm (TDEA) Block Cipher", NIST Special
              Publication 800-67, May 2008.

   [W3C.REC-xmlschema-2-20041028]
              Malhotra, A. and P. Biron, "XML Schema Part 2: Datatypes
              Second Edition", World Wide Web Consortium
              Recommendation REC-xmlschema-2-20041028, October 2004,
              <http://www.w3.org/TR/2004/REC-xmlschema-2-20041028>.

   [XMLDSIG]  Solo, D., Reagle, J., and D. Eastlake, "XML-Signature
              Syntax and Processing", World Wide Web Consortium
              FirstEdition REC-xmldsig-core-20020212, February 2002,
              <http://www.w3.org/TR/2002/REC-xmldsig-core-20020212>.

   [XMLENC]   Eastlake, D., "XML Encryption Syntax and Processing.",
              W3C Recommendation, December 2002,
              <http://www.w3.org/TR/xmlenc-core/>.

   [XMLENC11]
              Reagle, J. and D. Eastlake, "XML Encryption Syntax and
              Processing Version 1.1", World Wide Web Consortium WD WD-
              xmlenc-core1-20090730, July 2009,
              <http://www.w3.org/TR/2009/WD-xmlenc-core1-20090730>.

16.2.  Informative References

   [CAP]      MasterCard International, "Chip Authentication Program
              Functional Architecture", September 2004.

   [IPsec]    Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, December 2005.







Hoyer, et al.                Standards Track                   [Page 52]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   [NIST800-57]
              Barker, E., Barker, W., Burr, W., Polk, W., and M. Smid,
              "NIST Special Publication 800-57, Recommendation for Key
              Management Part 1: General (Revised)", NIST Special
              Publication 800-57, March 2007.

   [OATH]     "Initiative for Open AuTHentication",
              <http://www.openauthentication.org>.

   [PSKC-ALGORITHM-PROFILES]
              Hoyer, P., Pei, M., Machani, S., and A. Doherty,
              "Additional Portable Symmetric Key Container (PSKC)
              Algorithm Profiles", Work in Progress, May 2010.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [TLS]      Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

   [XMLNS]    Hollander, D., Bray, T., and A. Layman, "Namespaces in
              XML", World Wide Web Consortium FirstEdition REC-xml-
              names-19990114, January 1999,
              <http://www.w3.org/TR/1999/REC-xml-names-19990114>.






















Hoyer, et al.                Standards Track                   [Page 53]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


Appendix A.  Use Cases

   This section describes a comprehensive list of use cases that
   inspired the development of this specification.  These requirements
   were used to derive the primary requirement that drove the design.
   These requirements are covered in the next section.

   These use cases also help in understanding the applicability of this
   specification to real-world situations.

A.1.  Online Use Cases

   This section describes the use cases related to provisioning the keys
   using an online provisioning protocol.

A.1.1.  Transport of Keys from Server to Cryptographic Module

   For example, a mobile device user wants to obtain a symmetric key for
   use with a cryptographic module on the device.  The cryptographic
   module from vendor A initiates the provisioning process against a
   provisioning system from vendor B using a standards-based
   provisioning protocol.  The provisioning entity delivers one or more
   keys in a standard format that can be processed by the mobile device.

   For example, in a variation of the above, instead of the user's
   mobile phone, a key is provisioned in the user's soft token
   application on a laptop using a network-based online protocol.  As
   before, the provisioning system delivers a key in a standard format
   that can be processed by the soft token on the PC.

   For example, the end user or the key issuer wants to update or
   configure an existing key in the cryptographic module and requests a
   replacement key container.  The container may or may not include a
   new key and may include new or updated key attributes such as a new
   counter value in HOTP key case, a modified response format or length,
   a new friendly name, etc.

A.1.2.  Transport of Keys from Cryptographic Module to Cryptographic
        Module

   For example, a user wants to transport a key from one cryptographic
   module to another.  There may be two cryptographic modules, one on a
   computer and one on a mobile phone, and the user wants to transport a
   key from the computer to the mobile phone.  The user can export the
   key and related data in a standard format for input into the other
   cryptographic module.





Hoyer, et al.                Standards Track                   [Page 54]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


A.1.3.  Transport of Keys from Cryptographic Module to Server

   For example, a user wants to activate and use a new key and related
   data against a validation system that is not aware of this key.  This
   key may be embedded in the cryptographic module (e.g., a Secure
   Digital (SD) card, USB drive) that the user has purchased at the
   local electronics retailer.  Along with the cryptographic module, the
   user may get the key on a CD or a floppy in a standard format.  The
   user can now upload via a secure online channel or import this key
   and related data into the new validation system and start using the
   key.

A.1.4.  Server-to-Server Bulk Import/Export of Keys

   From time to time, a key management system may be required to import
   or export keys in bulk from one entity to another.

   For example, instead of importing keys from a manufacturer using a
   file, a validation server may download the keys using an online
   protocol.  The keys can be downloaded in a standard format that can
   be processed by a validation system.

   For example, in a variation of the above, an Over-The-Air (OTA) key
   provisioning gateway that provisions keys to mobile phones may obtain
   key material from a key issuer using an online protocol.  The keys
   are delivered in a standard format that can be processed by the key
   provisioning gateway and subsequently sent to the mobile phone of the
   end user.

A.2.  Offline Use Cases

   This section describes the use cases relating to offline transport of
   keys from one system to another, using some form of export and import
   model.

A.2.1.  Server-to-Server Bulk Import/Export of Keys

   For example, cryptographic modules, such as OTP authentication
   tokens, may have their symmetric keys initialized during the
   manufacturing process in bulk, requiring copies of the keys and
   algorithm data to be loaded into the authentication system through a
   file on portable media.  The manufacturer provides the keys and
   related data in the form of a file containing records in standard
   format, typically on a CD.  Note that the token manufacturer and the
   vendor for the validation system may be the same or different.  Some
   crypto modules will allow local PIN management (the device will have
   a PIN pad); hence, random initial PINs set at manufacturing should be
   transmitted together with the respective keys they protect.



Hoyer, et al.                Standards Track                   [Page 55]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   For example, an enterprise wants to port keys and related data from
   an existing validation system A into a different validation system B.
   The existing validation system provides the enterprise with a
   functionality that enables export of keys and related data (e.g., for
   OTP authentication tokens) in a standard format.  Since the OTP
   tokens are in the standard format, the enterprise can import the
   token records into the new validation system B and start using the
   existing tokens.  Note that the vendors for the two validation
   systems may be the same or different.

Appendix B.  Requirements

   This section outlines the most relevant requirements that are the
   basis of this work.  Several of the requirements were derived from
   use cases described above.

   R1:   The format MUST support the transport of multiple types of
         symmetric keys and related attributes for algorithms including
         HOTP, other OTP, Challenge/Response, etc.

   R2:   The format MUST handle the symmetric key itself as well of
         attributes that are typically associated with symmetric keys.
         Some of these attributes may be

         *  Unique Key Identifier

         *  Issuer information

         *  Algorithm ID

         *  Algorithm mode

         *  Issuer Name

         *  Key friendly name

         *  Event counter value (moving factor for OTP algorithms)

         *  Time value

   R3:   The format SHOULD support both offline and online scenarios.
         That is, it should be serializable to a file as well as it
         should be possible to use this format in online provisioning
         protocols.

   R4:   The format SHOULD allow bulk representation of symmetric keys.





Hoyer, et al.                Standards Track                   [Page 56]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


   R5:   The format SHOULD allow bulk representation of PINs related to
         specific keys.

   R6:   The format SHOULD be portable to various platforms.
         Furthermore, it SHOULD be computationally efficient to process.

   R7:   The format MUST provide an appropriate level of security in
         terms of data encryption and data integrity.

   R8:   For online scenarios, the format SHOULD NOT rely on transport
         layer security (e.g., Secure Socket Layer/Transport Layer
         Security (SSL/TLS)) for core security requirements.

   R9:   The format SHOULD be extensible.  It SHOULD enable extension
         points allowing vendors to specify additional attributes in the
         future.

   R10:  The format SHOULD allow for distribution of key derivation data
         without the actual symmetric key itself.  This is to support
         symmetric key management schemes that rely on key derivation
         algorithms based on a pre-placed master key.  The key
         derivation data typically consists of a reference to the key,
         rather than the key value itself.

   R11:  The format SHOULD allow for additional life cycle management
         operations such as counter resynchronization.  Such processes
         require confidentiality between client and server, thus could
         use a common secure container format, without the transfer of
         key material.

   R12:  The format MUST support the use of pre-shared symmetric keys to
         ensure confidentiality of sensitive data elements.

   R13:  The format MUST support a password-based encryption (PBE)
         [PKCS5] scheme to ensure security of sensitive data elements.
         This is a widely used method for various provisioning
         scenarios.

   R14:  The format SHOULD support asymmetric encryption algorithms such
         as RSA to ensure end-to-end security of sensitive data
         elements.  This is to support scenarios where a pre-set shared
         key encryption key is difficult to use.









Hoyer, et al.                Standards Track                   [Page 57]

RFC 6030         Portable Symmetric Key Container (PSKC)    October 2010


Authors' Addresses

   Philip Hoyer
   ActivIdentity, Inc.
   117 Waterloo Road
   London, SE1  8UL
   UK

   Phone: +44 (0) 20 7960 0220
   EMail: phoyer@actividentity.com


   Mingliang Pei
   VeriSign, Inc.
   487 E. Middlefield Road
   Mountain View, CA  94043
   USA

   Phone: +1 650 426 5173
   EMail: mpei@verisign.com


   Salah Machani
   Diversinet, Inc.
   2225 Sheppard Avenue East
   Suite 1801
   Toronto, Ontario  M2J 5C2
   Canada

   Phone: +1 416 756 2324 Ext. 321
   EMail: smachani@diversinet.com




















Hoyer, et al.                Standards Track                   [Page 58]

