Updated: 2022/Sep/29

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LIFE_CYCLE-DIGEST(7)                OpenSSL               LIFE_CYCLE-DIGEST(7)



NAME
       life_cycle-digest - The digest algorithm life-cycle

DESCRIPTION
       All message digests (MDs) go through a number of stages in their life-
       cycle:

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

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

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

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

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

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

   State Transition Diagram
       The usual life-cycle of a MD is illustrated:
                            +-------------------+
                            |       start       |
                            +-------------------+
                              |
                              | EVP_MD_CTX_new
                              v
                            +-------------------+         EVP_MD_CTX_reset
                            |       newed       |
       <------------------------------+
                            +-------------------+
       |
                              |
       |
                              | EVP_DigestInit
       |
                              v
       |
                            +-------------------+
       |
                       +--> |    initialised    | <+ EVP_DigestInit
       |
                       |    +-------------------+  |
       |
                       |      |                    |      EVP_DigestUpdate
       |
                       |      | EVP_DigestUpdate   |    +------------------+
       |
                       |      v                    |    v                  |
       |
                       |    +------------------------------------------------+
       |
        EVP_DigestInit |    |                    updated                     |
       --+
                       |    +------------------------------------------------+
       |
                       |      |                    |
       |
                       |      | EVP_DigestFinal    | EVP_DigestFinalXOF
       |
                       |      v                    v
       |
                       |    +------------------------------------------------+
       |
                       +--- |                    finaled                     |
       --+
                            +------------------------------------------------+
                              |
                              | EVP_MD_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_MD_CTX_new               newed
        EVP_DigestInit                    initialised initialised initialised
       initialised
        EVP_DigestUpdate                                updated     updated
        EVP_DigestFinal                                             finaled
        EVP_DigestFinalXOF                                          finaled
        EVP_MD_CTX_free              freed   freed       freed       freed
       freed
        EVP_MD_CTX_reset                     newed       newed       newed
       newed
        EVP_MD_CTX_get_params                newed    initialised   updated
        EVP_MD_CTX_set_params                newed    initialised   updated
        EVP_MD_CTX_gettable_params           newed    initialised   updated
        EVP_MD_CTX_settable_params           newed    initialised   updated

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

SEE ALSO
       provider-digest(7), EVP_DigestInit(3)

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>.



3.0.12                            2023-05-07              LIFE_CYCLE-DIGEST(7)