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<ul id="index">
<li><a href="#NAME">NAME</a></li>
<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
<li><a href="#NOTES">NOTES</a></li>
<li><a href="#RETURN-VALUES">RETURN VALUES</a></li>
<li><a href="#EXAMPLES">EXAMPLES</a></li>
<li><a href="#SEE-ALSO">SEE ALSO</a></li>
<li><a href="#HISTORY">HISTORY</a></li>
<li><a href="#COPYRIGHT">COPYRIGHT</a></li>
</ul>
<h1 id="NAME">NAME</h1>
<p>EVP_PKEY_sign_init, EVP_PKEY_sign - sign using a public key algorithm</p>
<h1 id="SYNOPSIS">SYNOPSIS</h1>
<pre><code> #include <openssl/evp.h>
int EVP_PKEY_sign_init(EVP_PKEY_CTX *ctx);
int EVP_PKEY_sign(EVP_PKEY_CTX *ctx,
unsigned char *sig, size_t *siglen,
const unsigned char *tbs, size_t tbslen);</code></pre>
<h1 id="DESCRIPTION">DESCRIPTION</h1>
<p>The EVP_PKEY_sign_init() function initializes a public key algorithm context using key <b>pkey</b> for a signing operation.</p>
<p>The EVP_PKEY_sign() function performs a public key signing operation using <b>ctx</b>. The data to be signed is specified using the <b>tbs</b> and <b>tbslen</b> parameters. If <b>sig</b> is <b>NULL</b> then the maximum size of the output buffer is written to the <b>siglen</b> parameter. If <b>sig</b> is not <b>NULL</b> then before the call the <b>siglen</b> parameter should contain the length of the <b>sig</b> buffer, if the call is successful the signature is written to <b>sig</b> and the amount of data written to <b>siglen</b>.</p>
<h1 id="NOTES">NOTES</h1>
<p>EVP_PKEY_sign() does not hash the data to be signed, and therefore is normally used to sign digests. For signing arbitrary messages, see the <a href="../man3/EVP_DigestSignInit.html">EVP_DigestSignInit(3)</a> and <a href="../man3/EVP_SignInit.html">EVP_SignInit(3)</a> signing interfaces instead.</p>
<p>After the call to EVP_PKEY_sign_init() algorithm specific control operations can be performed to set any appropriate parameters for the operation (see <a href="../man3/EVP_PKEY_CTX_ctrl.html">EVP_PKEY_CTX_ctrl(3)</a>).</p>
<p>The function EVP_PKEY_sign() can be called more than once on the same context if several operations are performed using the same parameters.</p>
<h1 id="RETURN-VALUES">RETURN VALUES</h1>
<p>EVP_PKEY_sign_init() and EVP_PKEY_sign() return 1 for success and 0 or a negative value for failure. In particular a return value of -2 indicates the operation is not supported by the public key algorithm.</p>
<h1 id="EXAMPLES">EXAMPLES</h1>
<p>Sign data using RSA with PKCS#1 padding and SHA256 digest:</p>
<pre><code> #include <openssl/evp.h>
#include <openssl/rsa.h>
EVP_PKEY_CTX *ctx;
/* md is a SHA-256 digest in this example. */
unsigned char *md, *sig;
size_t mdlen = 32, siglen;
EVP_PKEY *signing_key;
/*
* NB: assumes signing_key and md are set up before the next
* step. signing_key must be an RSA private key and md must
* point to the SHA-256 digest to be signed.
*/
ctx = EVP_PKEY_CTX_new(signing_key, NULL /* no engine */);
if (!ctx)
/* Error occurred */
if (EVP_PKEY_sign_init(ctx) <= 0)
/* Error */
if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0)
/* Error */
if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0)
/* Error */
/* Determine buffer length */
if (EVP_PKEY_sign(ctx, NULL, &siglen, md, mdlen) <= 0)
/* Error */
sig = OPENSSL_malloc(siglen);
if (!sig)
/* malloc failure */
if (EVP_PKEY_sign(ctx, sig, &siglen, md, mdlen) <= 0)
/* Error */
/* Signature is siglen bytes written to buffer sig */</code></pre>
<h1 id="SEE-ALSO">SEE ALSO</h1>
<p><a href="../man3/EVP_PKEY_CTX_new.html">EVP_PKEY_CTX_new(3)</a>, <a href="../man3/EVP_PKEY_CTX_ctrl.html">EVP_PKEY_CTX_ctrl(3)</a>, <a href="../man3/EVP_PKEY_encrypt.html">EVP_PKEY_encrypt(3)</a>, <a href="../man3/EVP_PKEY_decrypt.html">EVP_PKEY_decrypt(3)</a>, <a href="../man3/EVP_PKEY_verify.html">EVP_PKEY_verify(3)</a>, <a href="../man3/EVP_PKEY_verify_recover.html">EVP_PKEY_verify_recover(3)</a>, <a href="../man3/EVP_PKEY_derive.html">EVP_PKEY_derive(3)</a></p>
<h1 id="HISTORY">HISTORY</h1>
<p>These functions were added in OpenSSL 1.0.0.</p>
<h1 id="COPYRIGHT">COPYRIGHT</h1>
<p>Copyright 2006-2019 The OpenSSL Project Authors. All Rights Reserved.</p>
<p>Licensed under the OpenSSL license (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 <a href="https://www.openssl.org/source/license.html">https://www.openssl.org/source/license.html</a>.</p>
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