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<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="#copyright">COPYRIGHT</a></li>
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<h1><a name="name">NAME</a></h1>
<p>BIO_f_cipher, BIO_set_cipher, BIO_get_cipher_status, BIO_get_cipher_ctx - cipher BIO filter</p>
<p>
</p>
<hr />
<h1><a name="synopsis">SYNOPSIS</a></h1>
<pre>
#include <openssl/bio.h>
#include <openssl/evp.h></pre>
<pre>
const BIO_METHOD *BIO_f_cipher(void);
void BIO_set_cipher(BIO *b, const EVP_CIPHER *cipher,
unsigned char *key, unsigned char *iv, int enc);
int BIO_get_cipher_status(BIO *b)
int BIO_get_cipher_ctx(BIO *b, EVP_CIPHER_CTX **pctx)</pre>
<p>
</p>
<hr />
<h1><a name="description">DESCRIPTION</a></h1>
<p><code>BIO_f_cipher()</code> returns the cipher BIO method. This is a filter
BIO that encrypts any data written through it, and decrypts any data
read from it. It is a BIO wrapper for the cipher routines
<code>EVP_CipherInit()</code>, <code>EVP_CipherUpdate()</code> and <code>EVP_CipherFinal()</code>.</p>
<p>Cipher BIOs do not support <code>BIO_gets()</code> or <code>BIO_puts()</code>.</p>
<p><code>BIO_flush()</code> on an encryption BIO that is being written through is
used to signal that no more data is to be encrypted: this is used
to flush and possibly pad the final block through the BIO.</p>
<p><code>BIO_set_cipher()</code> sets the cipher of BIO <strong>b</strong> to <strong>cipher</strong> using key <strong>key</strong>
and IV <strong>iv</strong>. <strong>enc</strong> should be set to 1 for encryption and zero for
decryption.</p>
<p>When reading from an encryption BIO the final block is automatically
decrypted and checked when EOF is detected. <code>BIO_get_cipher_status()</code>
is a <code>BIO_ctrl()</code> macro which can be called to determine whether the
decryption operation was successful.</p>
<p><code>BIO_get_cipher_ctx()</code> is a <code>BIO_ctrl()</code> macro which retrieves the internal
BIO cipher context. The retrieved context can be used in conjunction
with the standard cipher routines to set it up. This is useful when
<code>BIO_set_cipher()</code> is not flexible enough for the applications needs.</p>
<p>
</p>
<hr />
<h1><a name="notes">NOTES</a></h1>
<p>When encrypting <code>BIO_flush()</code> <strong>must</strong> be called to flush the final block
through the BIO. If it is not then the final block will fail a subsequent
decrypt.</p>
<p>When decrypting an error on the final block is signaled by a zero
return value from the read operation. A successful decrypt followed
by EOF will also return zero for the final read. <code>BIO_get_cipher_status()</code>
should be called to determine if the decrypt was successful.</p>
<p>As always, if <code>BIO_gets()</code> or <code>BIO_puts()</code> support is needed then it can
be achieved by preceding the cipher BIO with a buffering BIO.</p>
<p>
</p>
<hr />
<h1><a name="return_values">RETURN VALUES</a></h1>
<p><code>BIO_f_cipher()</code> returns the cipher BIO method.</p>
<p><code>BIO_set_cipher()</code> does not return a value.</p>
<p><code>BIO_get_cipher_status()</code> returns 1 for a successful decrypt and 0
for failure.</p>
<p><code>BIO_get_cipher_ctx()</code> currently always returns 1.</p>
<p>
</p>
<hr />
<h1><a name="copyright">COPYRIGHT</a></h1>
<p>Copyright 2000-2016 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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