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<title>EVP_PKEY_decapsulate</title>
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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_decapsulate_init, EVP_PKEY_decapsulate - Key decapsulation using a private key algorithm</p>
<h1 id="SYNOPSIS">SYNOPSIS</h1>
<pre><code> #include <openssl/evp.h>
int EVP_PKEY_decapsulate_init(EVP_PKEY_CTX *ctx, const OSSL_PARAM params[]);
int EVP_PKEY_decapsulate(EVP_PKEY_CTX *ctx,
unsigned char *secret, size_t *secretlen,
const unsigned char *wrapped, size_t wrappedlen);</code></pre>
<h1 id="DESCRIPTION">DESCRIPTION</h1>
<p>The EVP_PKEY_decapsulate_init() function initializes a private key algorithm context <i>ctx</i> for a decapsulation operation and then sets the <i>params</i> on the context in the same way as calling <a href="../man3/EVP_PKEY_CTX_set_params.html">EVP_PKEY_CTX_set_params(3)</a>.</p>
<p>The EVP_PKEY_decapsulate() function performs a private key decapsulation operation using <i>ctx</i>. The data to be decapsulated is specified using the <i>wrapped</i> and <i>wrappedlen</i> parameters. If <i>secret</i> is <i>NULL</i> then the maximum size of the output secret buffer is written to the <i>*secretlen</i> parameter. If <i>secret</i> is not <b>NULL</b> and the call is successful then the decapsulated secret data is written to <i>secret</i> and the amount of data written to <i>secretlen</i>.</p>
<h1 id="NOTES">NOTES</h1>
<p>After the call to EVP_PKEY_decapsulate_init() algorithm specific parameters for the operation may be set or modified using <a href="../man3/EVP_PKEY_CTX_set_params.html">EVP_PKEY_CTX_set_params(3)</a>.</p>
<h1 id="RETURN-VALUES">RETURN VALUES</h1>
<p>EVP_PKEY_decapsulate_init() and EVP_PKEY_decapsulate() 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 private key algorithm.</p>
<h1 id="EXAMPLES">EXAMPLES</h1>
<p>Decapsulate data using RSA:</p>
<pre><code> #include <openssl/evp.h>
/*
* NB: assumes rsa_priv_key is an RSA private key,
* and that in, inlen are already set up to contain encapsulated data.
*/
EVP_PKEY_CTX *ctx = NULL;
size_t secretlen = 0;
unsigned char *secret = NULL;;
ctx = EVP_PKEY_CTX_new_from_pkey(libctx, rsa_priv_key, NULL);
if (ctx = NULL)
/* Error */
if (EVP_PKEY_decapsulate_init(ctx, NULL) <= 0)
/* Error */
/* Set the mode - only 'RSASVE' is currently supported */
if (EVP_PKEY_CTX_set_kem_op(ctx, "RSASVE") <= 0)
/* Error */
/* Determine buffer length */
if (EVP_PKEY_decapsulate(ctx, NULL, &secretlen, in, inlen) <= 0)
/* Error */
secret = OPENSSL_malloc(secretlen);
if (secret == NULL)
/* malloc failure */
/* Decapsulated secret data is secretlen bytes long */
if (EVP_PKEY_decapsulaterctx, secret, &secretlen, in, inlen) <= 0)
/* Error */</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_encapsulate.html">EVP_PKEY_encapsulate(3)</a>, <a href="../man7/EVP_KEM-RSA.html">EVP_KEM-RSA(7)</a>,</p>
<h1 id="HISTORY">HISTORY</h1>
<p>These functions were added in OpenSSL 3.0.</p>
<h1 id="COPYRIGHT">COPYRIGHT</h1>
<p>Copyright 2020-2021 The OpenSSL Project Authors. All Rights Reserved.</p>
<p>Licensed under the Apache License 2.0 (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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