=pod =head1 NAME life_cycle-kdf - The KDF algorithm life-cycle =head1 DESCRIPTION All key derivation functions (KDFs) and pseudo random functions (PRFs) go through a number of stages in their life-cycle: =over 4 =item start This state represents the KDF/PRF before it has been allocated. It is the starting state for any life-cycle transitions. =item newed This state represents the KDF/PRF after it has been allocated. =item deriving This state represents the KDF/PRF when it is set up and capable of generating output. =item freed This state is entered when the KDF/PRF is freed. It is the terminal state for all life-cycle transitions. =back =head2 State Transition Diagram The usual life-cycle of a KDF/PRF is illustrated: =begin man +-------------------+ | start | +-------------------+ | | EVP_KDF_CTX_new v +-------------------+ | newed | <+ +-------------------+ | | | | EVP_KDF_derive | v | EVP_KDF_CTX_reset EVP_KDF_derive +-------------------+ | + - - - - - - - - | | | ' | deriving | | + - - - - - - - -> | | -+ +-------------------+ | | EVP_KDF_CTX_free v +-------------------+ | freed | +-------------------+ =end man =for html =head2 Formal State Transitions This section defines all of the legal state transitions. This is the canonical list. =begin man Function Call ------------- Current State ------------- start newed deriving freed EVP_KDF_CTX_new newed EVP_KDF_derive deriving deriving EVP_KDF_CTX_free freed freed freed EVP_KDF_CTX_reset newed newed EVP_KDF_CTX_get_params newed deriving EVP_KDF_CTX_set_params newed deriving EVP_KDF_CTX_gettable_params newed deriving EVP_KDF_CTX_settable_params newed deriving =end man =begin html

Function Call | Current State
--- | ---
| start | newed | deriving | freed
EVP_KDF_CTX_new | newed |  |  |
EVP_KDF_derive |  | deriving | deriving |
EVP_KDF_CTX_free | freed | freed | freed |
EVP_KDF_CTX_reset |  | newed | newed |
EVP_KDF_CTX_get_params |  | newed | deriving |
EVP_KDF_CTX_set_params |  | newed | deriving |
EVP_KDF_CTX_gettable_params |  | newed | deriving |
EVP_KDF_CTX_settable_params |  | newed | deriving |

=end html =head1 NOTES At some point the EVP layer will begin enforcing the transitions described herein. =head1 SEE ALSO L, L. =head1 HISTORY The provider KDF interface was introduced in OpenSSL 3.0. =head1 COPYRIGHT Copyright 2021 The OpenSSL Project Authors. All Rights Reserved. Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at L. =cut