mirror of https://github.com/openssl/openssl
278 lines
15 KiB
Plaintext
278 lines
15 KiB
Plaintext
=pod
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=head1 NAME
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life_cycle-digest - The digest algorithm life-cycle
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=head1 DESCRIPTION
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All message digests (MDs) go through a number of stages in their life-cycle:
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=over 4
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=item start
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This state represents the MD before it has been allocated. It is the
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starting state for any life-cycle transitions.
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=item newed
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This state represents the MD after it has been allocated.
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=item initialised
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This state represents the MD when it is set up and capable of processing
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input.
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=item updated
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This state represents the MD when it is set up and capable of processing
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additional input or generating output.
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=item finaled
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This state represents the MD when it has generated output.
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For an XOF digest, this state represents the MD when it has generated a
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single-shot output.
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=item squeezed
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For an XOF digest, this state represents the MD when it has generated output.
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It can be called multiple times to generate more output. The output length is
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variable for each call.
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=item freed
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This state is entered when the MD is freed. It is the terminal state
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for all life-cycle transitions.
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=back
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=head2 State Transition Diagram
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The usual life-cycle of a MD is illustrated:
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=begin man
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+--------------------+
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| start |
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+--------------------+
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| EVP_MD_CTX_reset
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| EVP_MD_CTX_new +-------------------------------------------------+
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v v |
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EVP_MD_CTX_reset + - - - - - - - - - - - - - - - - - - - - - - + EVP_MD_CTX_reset |
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+-------------------> ' newed ' <--------------------+ |
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| + - - - - - - - - - - - - - - - - - - - - - - + | |
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| | | |
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| | EVP_DigestInit | |
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| v | |
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| EVP_DigestInit + - - - - - - - - - - - - - - - - - - - - - - + | |
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+----+-------------------> ' initialised ' <+ EVP_DigestInit | |
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| | + - - - - - - - - - - - - - - - - - - - - - - + | | |
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| | | ^ | | |
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| | | EVP_DigestUpdate | EVP_DigestInit | | |
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| | v | | | |
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| | +---------------------------------------------+ | | |
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| +-------------------- | | | | |
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| EVP_DigestUpdate | | | | |
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| +-------------------- | | | | |
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| | | updated | | | |
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| +-------------------> | | | | |
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| | | | | |
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+----+------------------------- | | -+-------------------+----+ |
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| | +---------------------------------------------+ | | | |
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| | | | | | |
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| | | EVP_DigestSqueeze +-------------------+ | | |
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| | v | | | |
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| | EVP_DigestSqueeze +---------------------------------------------+ | | |
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| | +-------------------- | | | | |
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| | | | squeezed | | | |
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| | +-------------------> | | ---------------------+ | |
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| | +---------------------------------------------+ | |
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| | | | |
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| | +---------------------------------------+ | |
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| | +---------------------------------------------+ EVP_DigestFinalXOF | | |
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| +------------------------- | finaled | <--------------------+----+ |
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| +---------------------------------------------+ | |
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| EVP_DigestFinal ^ | | | |
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+---------------------------------+ | | EVP_MD_CTX_free | |
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| v | |
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| +------------------+ EVP_MD_CTX_free | |
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| | freed | <--------------------+ |
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| +------------------+ |
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+------------------------------------------------------+
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=end man
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=for html <img src="img/digest.png">
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=head2 Formal State Transitions
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This section defines all of the legal state transitions.
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This is the canonical list.
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=begin man
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Function Call --------------------- Current State -----------------------------------
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start newed initialised updated finaled squeezed freed
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EVP_MD_CTX_new newed
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EVP_DigestInit initialised initialised initialised initialised initialised
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EVP_DigestUpdate updated updated
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EVP_DigestFinal finaled
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EVP_DigestFinalXOF finaled
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EVP_DigestSqueeze squeezed squeezed
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EVP_MD_CTX_free freed freed freed freed freed
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EVP_MD_CTX_reset newed newed newed newed
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EVP_MD_CTX_get_params newed initialised updated
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EVP_MD_CTX_set_params newed initialised updated
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EVP_MD_CTX_gettable_params newed initialised updated
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EVP_MD_CTX_settable_params newed initialised updated
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EVP_MD_CTX_copy_ex newed initialised updated squeezed
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=end man
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=begin html
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<table style="border:1px solid; border-collapse:collapse">
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<tr><th style="border:1px solid" align="left">Function Call</th>
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<th style="border:1px solid" colspan="6">Current State</th></tr>
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<tr><th style="border:1px solid"></th>
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<th style="border:1px solid" align="center">start</th>
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<th style="border:1px solid" align="center">newed</th>
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<th style="border:1px solid" align="center">initialised</th>
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<th style="border:1px solid" align="center">updated</th>
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<th style="border:1px solid" align="center">finaled</th>
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<th style="border:1px solid" align="center">squeezed</th>
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<th style="border:1px solid" align="center">freed</th></tr>
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<tr><th style="border:1px solid" align="left">EVP_MD_CTX_new</th>
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<td style="border:1px solid" align="center">newed</td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td></tr>
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<tr><th style="border:1px solid" align="left">EVP_DigestInit</th>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center">initialised</td>
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<td style="border:1px solid" align="center">initialised</td>
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<td style="border:1px solid" align="center">initialised</td>
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<td style="border:1px solid" align="center">initialised</td>
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<td style="border:1px solid" align="center">initialised</td>
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<td style="border:1px solid" align="center"></td></tr>
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<tr><th style="border:1px solid" align="left">EVP_DigestUpdate</th>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center">updated</td>
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<td style="border:1px solid" align="center">updated</td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td></tr>
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<tr><th style="border:1px solid" align="left">EVP_DigestFinal</th>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center">finaled</td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td></tr>
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<tr><th style="border:1px solid" align="left">EVP_DigestSqueeze</th>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center">squeezed</td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center">squeezed</td>
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<td style="border:1px solid" align="center"></td></tr>
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<tr><th style="border:1px solid" align="left">EVP_DigestFinalXOF</th>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center">finaled</td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td></tr>
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<tr><th style="border:1px solid" align="left">EVP_MD_CTX_free</th>
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<td style="border:1px solid" align="center">freed</td>
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<td style="border:1px solid" align="center">freed</td>
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<td style="border:1px solid" align="center">freed</td>
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<td style="border:1px solid" align="center">freed</td>
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<td style="border:1px solid" align="center">freed</td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td></tr>
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<tr><th style="border:1px solid" align="left">EVP_MD_CTX_reset</th>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center">newed</td>
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<td style="border:1px solid" align="center">newed</td>
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<td style="border:1px solid" align="center">newed</td>
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<td style="border:1px solid" align="center">newed</td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td></tr>
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<tr><th style="border:1px solid" align="left">EVP_MD_CTX_get_params</th>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center">newed</td>
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<td style="border:1px solid" align="center">initialised</td>
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<td style="border:1px solid" align="center">updated</td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td></tr>
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<tr><th style="border:1px solid" align="left">EVP_MD_CTX_set_params</th>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center">newed</td>
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<td style="border:1px solid" align="center">initialised</td>
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<td style="border:1px solid" align="center">updated</td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td></tr>
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<tr><th style="border:1px solid" align="left">EVP_MD_CTX_gettable_params</th>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center">newed</td>
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<td style="border:1px solid" align="center">initialised</td>
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<td style="border:1px solid" align="center">updated</td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td></tr>
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<tr><th style="border:1px solid" align="left">EVP_MD_CTX_settable_params</th>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center">newed</td>
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<td style="border:1px solid" align="center">initialised</td>
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<td style="border:1px solid" align="center">updated</td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center"></td></tr>
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<tr><th style="border:1px solid" align="left">EVP_MD_CTX_copy_ex</th>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center">newed</td>
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<td style="border:1px solid" align="center">initialised</td>
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<td style="border:1px solid" align="center">updated</td>
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<td style="border:1px solid" align="center"></td>
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<td style="border:1px solid" align="center">squeezed</td>
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<td style="border:1px solid" align="center"></td></tr>
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</table>
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=end html
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=head1 NOTES
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At some point the EVP layer will begin enforcing the transitions described
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herein.
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=head1 SEE ALSO
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L<provider-digest(7)>, L<EVP_DigestInit(3)>
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=head1 COPYRIGHT
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Copyright 2021-2023 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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