Android_verify/third_party/android-libs/share/man/man7/life_cycle-digest.7ossl

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.\" ========================================================================
.\"
.IX Title "LIFE_CYCLE-DIGEST 7ossl"
.TH LIFE_CYCLE-DIGEST 7ossl "2024-09-03" "3.3.2" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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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>.