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<p><a name="__index__"></a></p>
<ul>
<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="#see_also">SEE ALSO</a></li>
<li><a href="#copyright">COPYRIGHT</a></li>
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<h1><a name="name">NAME</a></h1>
<p>EVP_OpenInit, EVP_OpenUpdate, EVP_OpenFinal - EVP envelope decryption</p>
<p>
</p>
<hr />
<h1><a name="synopsis">SYNOPSIS</a></h1>
<pre>
#include <openssl/evp.h></pre>
<pre>
int EVP_OpenInit(EVP_CIPHER_CTX *ctx, EVP_CIPHER *type, unsigned char *ek,
int ekl, unsigned char *iv, EVP_PKEY *priv);
int EVP_OpenUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
int *outl, unsigned char *in, int inl);
int EVP_OpenFinal(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);</pre>
<p>
</p>
<hr />
<h1><a name="description">DESCRIPTION</a></h1>
<p>The EVP envelope routines are a high-level interface to envelope
decryption. They decrypt a public key encrypted symmetric key and
then decrypt data using it.</p>
<p><code>EVP_OpenInit()</code> initializes a cipher context <strong>ctx</strong> for decryption
with cipher <strong>type</strong>. It decrypts the encrypted symmetric key of length
<strong>ekl</strong> bytes passed in the <strong>ek</strong> parameter using the private key <strong>priv</strong>.
The IV is supplied in the <strong>iv</strong> parameter.</p>
<p><code>EVP_OpenUpdate()</code> and <code>EVP_OpenFinal()</code> have exactly the same properties
as the <code>EVP_DecryptUpdate()</code> and <code>EVP_DecryptFinal()</code> routines, as
documented on the <em>EVP_EncryptInit(3)</em> manual
page.</p>
<p>
</p>
<hr />
<h1><a name="notes">NOTES</a></h1>
<p>It is possible to call <code>EVP_OpenInit()</code> twice in the same way as
<code>EVP_DecryptInit()</code>. The first call should have <strong>priv</strong> set to NULL
and (after setting any cipher parameters) it should be called again
with <strong>type</strong> set to NULL.</p>
<p>If the cipher passed in the <strong>type</strong> parameter is a variable length
cipher then the key length will be set to the value of the recovered
key length. If the cipher is a fixed length cipher then the recovered
key length must match the fixed cipher length.</p>
<p>
</p>
<hr />
<h1><a name="return_values">RETURN VALUES</a></h1>
<p><code>EVP_OpenInit()</code> returns 0 on error or a non zero integer (actually the
recovered secret key size) if successful.</p>
<p><code>EVP_OpenUpdate()</code> returns 1 for success or 0 for failure.</p>
<p><code>EVP_OpenFinal()</code> returns 0 if the decrypt failed or 1 for success.</p>
<p>
</p>
<hr />
<h1><a name="see_also">SEE ALSO</a></h1>
<p><em>evp(7)</em>, <em>RAND_bytes(3)</em>,
<em>EVP_EncryptInit(3)</em>,
<em>EVP_SealInit(3)</em></p>
<p>
</p>
<hr />
<h1><a name="copyright">COPYRIGHT</a></h1>
<p>Copyright 2000-2020 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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