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life_cycle-mac - The MAC algorithm life-cycle


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

This state represents the MAC before it has been allocated. It is the starting state for any life-cycle transitions.
This state represents the MAC after it has been allocated.
This state represents the MAC when it is set up and capable of processing input.
This state represents the MAC when it is set up and capable of processing additional input or generating output.
This state represents the MAC when it has generated output.
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 |
| newed |
| EVP_MAC_init
+> | 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
| 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


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


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


The provider MAC interface was introduced in OpenSSL 3.0.


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 <>.

2022-08-14 3.0.5