LIFE_CYCLE-MAC(7ossl)

NAME
life_cycle-mac - The MAC algorithm life-cycle

DESCRIPTION
All message authentication codes (MACs) go through a number of stages in their life-cycle:

start
    This state represents the MAC before it has been allocated. It is the starting state for any life-cycle transitions.

newed
    This state represents the MAC after it has been allocated.

initialised
    This state represents the MAC when it is set up and capable of processing input.

updated
    This state represents the MAC when it is set up and capable of processing additional input or generating output.

finaled
    This state represents the MAC when it has generated output.

freed
    This state is entered when the MAC is freed. It is the terminal state for all life-cycle transitions.

  State Transition Diagram
The usual life-cycle of a MAC is illustrated:
                 +-------------------+
                 | start |
                 +-------------------+
                   |
                   | EVP_MAC_CTX_new
                   v
                 +-------------------+
                 | newed |
                 +-------------------+
                   |
                   | EVP_MAC_init
                   v
                 +-------------------+
              +> | initialised | <+
              | +-------------------+ |
              | | |
              | | EVP_MAC_update | EVP_MAC_init
              | v |
 EVP_MAC_init | +-------------------+ |
              | | updated | -+
              | +-------------------+
              | | |
              | | EVP_MAC_final | EVP_MAC_finalXOF
              | v v
              | +-------------------+
              +- | finaled |
                 +-------------------+
                   |
                   | EVP_MAC_CTX_free
                   v
                 +-------------------+
                 | freed |
                 +-------------------+

  Formal State Transitions
This section defines all of the legal state transitions. This is the canonical list.
 Function Call --------------------- Current State ----------------------
                        start newed initialised updated finaled freed
 EVP_MAC_CTX_new newed
 EVP_MAC_init initialised initialised initialised initialised
 EVP_MAC_update updated updated
 EVP_MAC_final finaled
 EVP_MAC_finalXOF finaled
 EVP_MAC_CTX_free freed freed freed freed freed
 EVP_MAC_CTX_get_params newed initialised updated
 EVP_MAC_CTX_set_params newed initialised updated
 EVP_MAC_CTX_gettable_params newed initialised updated
 EVP_MAC_CTX_settable_params newed initialised updated

NOTES
At some point the EVP layer will begin enforcing the transitions described herein.

SEE ALSO
provider-mac(7), EVP_MAC(3).

HISTORY
The provider MAC interface was introduced in OpenSSL 3.0.

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 <https://www.openssl.org/source/license.html>.