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.\"
.IX Title "LIFE_CYCLE-DIGEST 7ossl"
.TH LIFE_CYCLE-DIGEST 7ossl "2024-10-22" "3.4.0" "OpenSSL"
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.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 \s-1MD\s0 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 \s-1MD\s0 after it has been allocated.
.IP "initialised" 4
.IX Item "initialised"
This state represents the \s-1MD\s0 when it is set up and capable of processing
input.
.IP "updated" 4
.IX Item "updated"
This state represents the \s-1MD\s0 when it is set up and capable of processing
additional input or generating output.
.IP "finaled" 4
.IX Item "finaled"
This state represents the \s-1MD\s0 when it has generated output.
For an \s-1XOF\s0 digest, this state represents the \s-1MD\s0 when it has generated a
single-shot output.
.IP "squeezed" 4
.IX Item "squeezed"
For an \s-1XOF\s0 digest, this state represents the \s-1MD\s0 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 \s-1MD\s0 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 \s-1MD\s0 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 \s-1EVP\s0 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 \*(L"License\*(R"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.