222 lines
10 KiB
HTML
Executable File
222 lines
10 KiB
HTML
Executable File
<?xml version="1.0" ?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<title>EVP_DigestSignInit</title>
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<meta http-equiv="content-type" content="text/html; charset=utf-8" />
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<link rev="made" href="mailto:root@localhost" />
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</head>
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<body style="background-color: white">
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<!-- INDEX BEGIN -->
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<div name="index">
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<p><a name="__index__"></a></p>
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<ul>
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<li><a href="#name">NAME</a></li>
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<li><a href="#synopsis">SYNOPSIS</a></li>
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<li><a href="#description">DESCRIPTION</a></li>
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<li><a href="#return_values">RETURN VALUES</a></li>
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<li><a href="#notes">NOTES</a></li>
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<li><a href="#see_also">SEE ALSO</a></li>
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<li><a href="#history">HISTORY</a></li>
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<li><a href="#copyright">COPYRIGHT</a></li>
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</ul>
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<hr name="index" />
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</div>
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<!-- INDEX END -->
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<p>
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</p>
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<hr />
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<h1><a name="name">NAME</a></h1>
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<p>EVP_DigestSignInit_ex, EVP_DigestSignInit, EVP_DigestSignUpdate,
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EVP_DigestSignFinal, EVP_DigestSign - EVP signing functions</p>
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<p>
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</p>
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<hr />
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<h1><a name="synopsis">SYNOPSIS</a></h1>
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<pre>
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#include <openssl/evp.h></pre>
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<pre>
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int EVP_DigestSignInit_ex(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx,
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const char *mdname, const char *props,
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EVP_PKEY *pkey);
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int EVP_DigestSignInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx,
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const EVP_MD *type, ENGINE *e, EVP_PKEY *pkey);
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int EVP_DigestSignUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt);
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int EVP_DigestSignFinal(EVP_MD_CTX *ctx, unsigned char *sig, size_t *siglen);</pre>
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<pre>
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int EVP_DigestSign(EVP_MD_CTX *ctx, unsigned char *sigret,
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size_t *siglen, const unsigned char *tbs,
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size_t tbslen);</pre>
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<p>
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</p>
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<hr />
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<h1><a name="description">DESCRIPTION</a></h1>
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<p>The EVP signature routines are a high level interface to digital signatures.
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Input data is digested first before the signing takes place.</p>
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<p><code>EVP_DigestSignInit_ex()</code> sets up signing context <em>ctx</em> to use a digest with the
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name <em>mdname</em> and private key <em>pkey</em>. The name of the digest to be used is
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passed to the provider of the signature algorithm in use. How that provider
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interprets the digest name is provider specific. The provider may implement
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that digest directly itself or it may (optionally) choose to fetch it (which
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could result in a digest from a different provider being selected). If the
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provider supports fetching the digest then it may use the <em>props</em> argument for
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the properties to be used during the fetch.</p>
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<p>The <em>pkey</em> algorithm is used to fetch a <strong>EVP_SIGNATURE</strong> method implicitly, to
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be used for the actual signing. See <em>provider(7)/Implicit fetch</em> for
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more information about implict fetches.</p>
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<p>The OpenSSL default and legacy providers support fetching digests and can fetch
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those digests from any available provider. The OpenSSL fips provider also
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supports fetching digests but will only fetch digests that are themselves
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implemented inside the fips provider.</p>
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<p><em>ctx</em> must be created with <code>EVP_MD_CTX_new()</code> before calling this function. If
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<em>pctx</em> is not NULL, the EVP_PKEY_CTX of the signing operation will be written
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to <em>*pctx</em>: this can be used to set alternative signing options. Note that any
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existing value in <em>*pctx</em> is overwritten. The EVP_PKEY_CTX value returned must
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not be freed directly by the application if <em>ctx</em> is not assigned an
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EVP_PKEY_CTX value before being passed to <code>EVP_DigestSignInit_ex()</code> (which means
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the EVP_PKEY_CTX is created inside <code>EVP_DigestSignInit_ex()</code> and it will be freed
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automatically when the EVP_MD_CTX is freed).</p>
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<p>The digest <em>mdname</em> may be NULL if the signing algorithm supports it. The
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<em>props</em> argument can always be NULL.</p>
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<p>No <strong>EVP_PKEY_CTX</strong> will be created by <code>EVP_DigestSignInit_ex()</code> if the passed
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<em>ctx</em> has already been assigned one via <em>EVP_MD_CTX_set_pkey_ctx(3)</em>. See also
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<em>SM2(7)</em>.</p>
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<p>Only EVP_PKEY types that support signing can be used with these functions. This
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includes MAC algorithms where the MAC generation is considered as a form of
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"signing". Built-in EVP_PKEY types supported by these functions are CMAC,
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Poly1305, DSA, ECDSA, HMAC, RSA, SipHash, Ed25519 and Ed448.</p>
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<p>Not all digests can be used for all key types. The following combinations apply.</p>
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<dl>
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<dt><strong><a name="dsa" class="item">DSA</a></strong></dt>
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<dd>
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<p>Supports SHA1, SHA224, SHA256, SHA384 and SHA512</p>
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</dd>
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<dt><strong><a name="ecdsa" class="item">ECDSA</a></strong></dt>
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<dd>
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<p>Supports SHA1, SHA224, SHA256, SHA384, SHA512 and SM3</p>
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</dd>
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<dt><strong><a name="rsa_with_no_padding" class="item">RSA with no padding</a></strong></dt>
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<dd>
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<p>Supports no digests (the digest <em>type</em> must be NULL)</p>
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</dd>
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<dt><strong><a name="rsa_with_x931_padding" class="item">RSA with X931 padding</a></strong></dt>
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<dd>
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<p>Supports SHA1, SHA256, SHA384 and SHA512</p>
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</dd>
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<dt><strong><a name="all_other_rsa_padding_types" class="item">All other RSA padding types</a></strong></dt>
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<dd>
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<p>Support SHA1, SHA224, SHA256, SHA384, SHA512, MD5, MD5_SHA1, MD2, MD4, MDC2,
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SHA3-224, SHA3-256, SHA3-384, SHA3-512</p>
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</dd>
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<dt><strong><a name="ed25519_and_ed448" class="item">Ed25519 and Ed448</a></strong></dt>
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<dd>
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<p>Support no digests (the digest <em>type</em> must be NULL)</p>
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</dd>
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<dt><strong><a name="hmac" class="item">HMAC</a></strong></dt>
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<dd>
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<p>Supports any digest</p>
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</dd>
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<dt><strong><a name="cmac_poly1305_and_siphash" class="item">CMAC, Poly1305 and SipHash</a></strong></dt>
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<dd>
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<p>Will ignore any digest provided.</p>
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</dd>
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</dl>
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<p>If RSA-PSS is used and restrictions apply then the digest must match.</p>
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<p><code>EVP_DigestSignInit()</code> works in the same way as <code>EVP_DigestSignInit_ex()</code> except
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that the <em>mdname</em> parameter will be inferred from the supplied digest <em>type</em>,
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and <em>props</em> will be NULL. Where supplied the ENGINE <em>e</em> will be used for the
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signing and digest algorithm implementations. <em>e</em> may be NULL.</p>
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<p><code>EVP_DigestSignUpdate()</code> hashes <em>cnt</em> bytes of data at <em>d</em> into the
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signature context <em>ctx</em>. This function can be called several times on the
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same <em>ctx</em> to include additional data.</p>
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<p><code>EVP_DigestSignFinal()</code> signs the data in <em>ctx</em> and places the signature in <em>sig</em>.
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If <em>sig</em> is NULL then the maximum size of the output buffer is written to
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the <em>siglen</em> parameter. If <em>sig</em> is not NULL then before the call the
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<em>siglen</em> parameter should contain the length of the <em>sig</em> buffer. If the
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call is successful the signature is written to <em>sig</em> and the amount of data
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written to <em>siglen</em>.</p>
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<p><code>EVP_DigestSign()</code> signs <em>tbslen</em> bytes of data at <em>tbs</em> and places the
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signature in <em>sig</em> and its length in <em>siglen</em> in a similar way to
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<code>EVP_DigestSignFinal()</code>.</p>
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<p>
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</p>
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<hr />
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<h1><a name="return_values">RETURN VALUES</a></h1>
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<p><code>EVP_DigestSignInit()</code>, <code>EVP_DigestSignUpdate()</code>, <code>EVP_DigestSignFinal()</code> and
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<code>EVP_DigestSign()</code> return 1 for success and 0 for failure.</p>
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<p>The error codes can be obtained from <em>ERR_get_error(3)</em>.</p>
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<p>
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</p>
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<hr />
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<h1><a name="notes">NOTES</a></h1>
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<p>The <strong>EVP</strong> interface to digital signatures should almost always be used in
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preference to the low level interfaces. This is because the code then becomes
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transparent to the algorithm used and much more flexible.</p>
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<p><code>EVP_DigestSign()</code> is a one shot operation which signs a single block of data
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in one function. For algorithms that support streaming it is equivalent to
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calling <code>EVP_DigestSignUpdate()</code> and <code>EVP_DigestSignFinal()</code>. For algorithms which
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do not support streaming (e.g. PureEdDSA) it is the only way to sign data.</p>
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<p>In previous versions of OpenSSL there was a link between message digest types
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and public key algorithms. This meant that "clone" digests such as EVP_dss1()
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needed to be used to sign using SHA1 and DSA. This is no longer necessary and
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the use of clone digest is now discouraged.</p>
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<p>For some key types and parameters the random number generator must be seeded.
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If the automatic seeding or reseeding of the OpenSSL CSPRNG fails due to
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external circumstances (see <em>RAND(7)</em>), the operation will fail.</p>
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<p>The call to <code>EVP_DigestSignFinal()</code> internally finalizes a copy of the digest
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context. This means that calls to <code>EVP_DigestSignUpdate()</code> and
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<code>EVP_DigestSignFinal()</code> can be called later to digest and sign additional data.</p>
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<p>Since only a copy of the digest context is ever finalized, the context must
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be cleaned up after use by calling <code>EVP_MD_CTX_free()</code> or a memory leak
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will occur.</p>
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<p>The use of <code>EVP_PKEY_size()</code> with these functions is discouraged because some
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signature operations may have a signature length which depends on the
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parameters set. As a result <code>EVP_PKEY_size()</code> would have to return a value
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which indicates the maximum possible signature for any set of parameters.</p>
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<p>
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</p>
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<hr />
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<h1><a name="see_also">SEE ALSO</a></h1>
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<p><em>EVP_DigestVerifyInit(3)</em>,
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<em>EVP_DigestInit(3)</em>,
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<em>evp(7)</em>, <a href="#hmac">HMAC(3)</a>, <em>MD2(3)</em>,
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<em>MD5(3)</em>, <em>MDC2(3)</em>, <em>RIPEMD160(3)</em>,
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<em>SHA1(3)</em>, <em>openssl-dgst(1)</em>,
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<em>RAND(7)</em></p>
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<p>
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</p>
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<hr />
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<h1><a name="history">HISTORY</a></h1>
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<p><code>EVP_DigestSignInit()</code>, <code>EVP_DigestSignUpdate()</code> and <code>EVP_DigestSignFinal()</code>
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were added in OpenSSL 1.0.0.</p>
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<p><code>EVP_DigestSignInit_ex()</code> was added in OpenSSL 3.0.</p>
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<p><code>EVP_DigestSignUpdate()</code> was converted from a macro to a function in OpenSSL 3.0.</p>
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<p>
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</p>
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<hr />
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<h1><a name="copyright">COPYRIGHT</a></h1>
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<p>Copyright 2006-2018 The OpenSSL Project Authors. All Rights Reserved.</p>
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<p>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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<a href="https://www.openssl.org/source/license.html">https://www.openssl.org/source/license.html</a>.</p>
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</body>
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</html>
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