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- .\" -*- mode: troff; coding: utf-8 -*-
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- .IX Title "LIFE_CYCLE-DIGEST 7ossl"
- .TH LIFE_CYCLE-DIGEST 7ossl 2025-01-17 3.4.0 OpenSSL
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- .nh
- .SH NAME
- life_cycle\-digest \- The digest algorithm life\-cycle
- .SH DESCRIPTION
- .IX Header "DESCRIPTION"
- All message digests (MDs) go through a number of stages in their life-cycle:
- .IP start 4
- .IX Item "start"
- This state represents the MD before it has been allocated. It is the
- starting state for any life-cycle transitions.
- .IP newed 4
- .IX Item "newed"
- This state represents the MD after it has been allocated.
- .IP initialised 4
- .IX Item "initialised"
- This state represents the MD when it is set up and capable of processing
- input.
- .IP updated 4
- .IX Item "updated"
- This state represents the MD when it is set up and capable of processing
- additional input or generating output.
- .IP finaled 4
- .IX Item "finaled"
- This state represents the MD when it has generated output.
- For an XOF digest, this state represents the MD when it has generated a
- single-shot output.
- .IP squeezed 4
- .IX Item "squeezed"
- For an XOF digest, this state represents the MD when it has generated output.
- It can be called multiple times to generate more output. The output length is
- variable for each call.
- .IP freed 4
- .IX Item "freed"
- This state is entered when the MD is freed. It is the terminal state
- for all life-cycle transitions.
- .SS "State Transition Diagram"
- .IX Subsection "State Transition Diagram"
- The usual life-cycle of a MD is illustrated:
- +--------------------+
- | start |
- +--------------------+
- | EVP_MD_CTX_reset
- | EVP_MD_CTX_new +-------------------------------------------------+
- v v |
- EVP_MD_CTX_reset + - - - - - - - - - - - - - - - - - - - - - - + EVP_MD_CTX_reset |
- +-------------------> ' newed ' <--------------------+ |
- | + - - - - - - - - - - - - - - - - - - - - - - + | |
- | | | |
- | | EVP_DigestInit | |
- | v | |
- | EVP_DigestInit + - - - - - - - - - - - - - - - - - - - - - - + | |
- +----+-------------------> ' initialised ' <+ EVP_DigestInit | |
- | | + - - - - - - - - - - - - - - - - - - - - - - + | | |
- | | | ^ | | |
- | | | EVP_DigestUpdate | EVP_DigestInit | | |
- | | v | | | |
- | | +---------------------------------------------+ | | |
- | +-------------------- | | | | |
- | | | | | |
- | EVP_DigestUpdate | | | | |
- | +-------------------- | | | | |
- | | | updated | | | |
- | +-------------------> | | | | |
- | | | | | |
- | | | | | |
- +----+------------------------- | | -+-------------------+----+ |
- | | +---------------------------------------------+ | | | |
- | | | | | | |
- | | | EVP_DigestSqueeze +-------------------+ | | |
- | | v | | | |
- | | EVP_DigestSqueeze +---------------------------------------------+ | | |
- | | +-------------------- | | | | |
- | | | | squeezed | | | |
- | | +-------------------> | | ---------------------+ | |
- | | +---------------------------------------------+ | |
- | | | | |
- | | +---------------------------------------+ | |
- | | | | |
- | | +---------------------------------------------+ EVP_DigestFinalXOF | | |
- | +------------------------- | finaled | <--------------------+----+ |
- | +---------------------------------------------+ | |
- | EVP_DigestFinal ^ | | | |
- +---------------------------------+ | | EVP_MD_CTX_free | |
- | v | |
- | +------------------+ EVP_MD_CTX_free | |
- | | freed | <--------------------+ |
- | +------------------+ |
- | |
- +------------------------------------------------------+
- .SS "Formal State Transitions"
- .IX Subsection "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 squeezed freed
- EVP_MD_CTX_new newed
- EVP_DigestInit initialised initialised initialised initialised initialised
- EVP_DigestUpdate updated updated
- EVP_DigestFinal finaled
- EVP_DigestFinalXOF finaled
- EVP_DigestSqueeze squeezed squeezed
- 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
- EVP_MD_CTX_copy_ex newed initialised updated squeezed
- .SH NOTES
- .IX Header "NOTES"
- At some point the EVP layer will begin enforcing the transitions described
- herein.
- .SH "SEE ALSO"
- .IX Header "SEE ALSO"
- \&\fBprovider\-digest\fR\|(7), \fBEVP_DigestInit\fR\|(3)
- .SH COPYRIGHT
- .IX Header "COPYRIGHT"
- Copyright 2021\-2023 The OpenSSL Project Authors. All Rights Reserved.
- .PP
- 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>.
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