115 lines
4.2 KiB
HTML
Executable File
115 lines
4.2 KiB
HTML
Executable File
<?xml version="1.0" ?>
|
|
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
|
|
<html xmlns="http://www.w3.org/1999/xhtml">
|
|
<head>
|
|
<title>EVP_BytesToKey</title>
|
|
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
|
|
<link rev="made" href="mailto:root@localhost" />
|
|
</head>
|
|
|
|
<body style="background-color: white">
|
|
|
|
|
|
<!-- INDEX BEGIN -->
|
|
<div name="index">
|
|
<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="#key_derivation_algorithm">KEY DERIVATION ALGORITHM</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>
|
|
</ul>
|
|
|
|
<hr name="index" />
|
|
</div>
|
|
<!-- INDEX END -->
|
|
|
|
<p>
|
|
</p>
|
|
<hr />
|
|
<h1><a name="name">NAME</a></h1>
|
|
<p>EVP_BytesToKey - password based encryption routine</p>
|
|
<p>
|
|
</p>
|
|
<hr />
|
|
<h1><a name="synopsis">SYNOPSIS</a></h1>
|
|
<pre>
|
|
#include <openssl/evp.h></pre>
|
|
<pre>
|
|
int EVP_BytesToKey(const EVP_CIPHER *type, const EVP_MD *md,
|
|
const unsigned char *salt,
|
|
const unsigned char *data, int datal, int count,
|
|
unsigned char *key, unsigned char *iv);</pre>
|
|
<p>
|
|
</p>
|
|
<hr />
|
|
<h1><a name="description">DESCRIPTION</a></h1>
|
|
<p><code>EVP_BytesToKey()</code> derives a key and IV from various parameters. <strong>type</strong> is
|
|
the cipher to derive the key and IV for. <strong>md</strong> is the message digest to use.
|
|
The <strong>salt</strong> parameter is used as a salt in the derivation: it should point to
|
|
an 8 byte buffer or NULL if no salt is used. <strong>data</strong> is a buffer containing
|
|
<strong>datal</strong> bytes which is used to derive the keying data. <strong>count</strong> is the
|
|
iteration count to use. The derived key and IV will be written to <strong>key</strong>
|
|
and <strong>iv</strong> respectively.</p>
|
|
<p>
|
|
</p>
|
|
<hr />
|
|
<h1><a name="notes">NOTES</a></h1>
|
|
<p>A typical application of this function is to derive keying material for an
|
|
encryption algorithm from a password in the <strong>data</strong> parameter.</p>
|
|
<p>Increasing the <strong>count</strong> parameter slows down the algorithm which makes it
|
|
harder for an attacker to perform a brute force attack using a large number
|
|
of candidate passwords.</p>
|
|
<p>If the total key and IV length is less than the digest length and
|
|
<strong>MD5</strong> is used then the derivation algorithm is compatible with PKCS#5 v1.5
|
|
otherwise a non standard extension is used to derive the extra data.</p>
|
|
<p>Newer applications should use a more modern algorithm such as PBKDF2 as
|
|
defined in PKCS#5v2.1 and provided by PKCS5_PBKDF2_HMAC.</p>
|
|
<p>
|
|
</p>
|
|
<hr />
|
|
<h1><a name="key_derivation_algorithm">KEY DERIVATION ALGORITHM</a></h1>
|
|
<p>The key and IV is derived by concatenating D_1, D_2, etc until
|
|
enough data is available for the key and IV. D_i is defined as:</p>
|
|
<pre>
|
|
D_i = HASH^count(D_(i-1) || data || salt)</pre>
|
|
<p>where || denotes concatenation, D_0 is empty, HASH is the digest
|
|
algorithm in use, HASH^1(data) is simply HASH(data), HASH^2(data)
|
|
is HASH(HASH(data)) and so on.</p>
|
|
<p>The initial bytes are used for the key and the subsequent bytes for
|
|
the IV.</p>
|
|
<p>
|
|
</p>
|
|
<hr />
|
|
<h1><a name="return_values">RETURN VALUES</a></h1>
|
|
<p>If <strong>data</strong> is NULL, then <code>EVP_BytesToKey()</code> returns the number of bytes
|
|
needed to store the derived key.
|
|
Otherwise, <code>EVP_BytesToKey()</code> returns the size of the derived key in bytes,
|
|
or 0 on error.</p>
|
|
<p>
|
|
</p>
|
|
<hr />
|
|
<h1><a name="see_also">SEE ALSO</a></h1>
|
|
<p><em>evp(7)</em>, <em>RAND_bytes(3)</em>,
|
|
<em>PKCS5_PBKDF2_HMAC(3)</em>,
|
|
<em>EVP_EncryptInit(3)</em></p>
|
|
<p>
|
|
</p>
|
|
<hr />
|
|
<h1><a name="copyright">COPYRIGHT</a></h1>
|
|
<p>Copyright 2001-2016 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>
|
|
|
|
</body>
|
|
|
|
</html>
|