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<?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>DH_generate_key</title> <meta http-equiv="content-type" content="text/html; charset=utf-8" /> <link rev="made" href="mailto:root@hsxx.drive.ne.jp" /> </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="#return_values">RETURN VALUES</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> <hr name="index" /> </div> <!-- INDEX END --> <p> </p> <hr /> <h1><a name="name">NAME</a></h1> <p>DH_generate_key, DH_compute_key, DH_compute_key_padded - perform Diffie-Hellman key exchange</p> <p> </p> <hr /> <h1><a name="synopsis">SYNOPSIS</a></h1> <pre> #include <openssl/dh.h></pre> <pre> int DH_generate_key(DH *dh);</pre> <pre> int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh);</pre> <pre> int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh);</pre> <p> </p> <hr /> <h1><a name="description">DESCRIPTION</a></h1> <p><code>DH_generate_key()</code> performs the first step of a Diffie-Hellman key exchange by generating private and public DH values. By calling <code>DH_compute_key()</code> or <code>DH_compute_key_padded()</code>, these are combined with the other party's public value to compute the shared key.</p> <p><code>DH_generate_key()</code> expects <strong>dh</strong> to contain the shared parameters <strong>dh->p</strong> and <strong>dh->g</strong>. It generates a random private DH value unless <strong>dh->priv_key</strong> is already set, and computes the corresponding public value <strong>dh->pub_key</strong>, which can then be published.</p> <p><code>DH_compute_key()</code> computes the shared secret from the private DH value in <strong>dh</strong> and the other party's public value in <strong>pub_key</strong> and stores it in <strong>key</strong>. <strong>key</strong> must point to <strong>DH_size(dh)</strong> bytes of memory. The padding style is <a href="http://www.ietf.org/rfc/rfc5246.txt" class="rfc">RFC 5246</a> (8.1.2) that strips leading zero bytes. It is not constant time due to the leading zero bytes being stripped. The return value should be considered public.</p> <p><code>DH_compute_key_padded()</code> is similar but stores a fixed number of bytes. The padding style is NIST SP 800-56A (C.1) that retains leading zero bytes. It is constant time due to the leading zero bytes being retained. The return value should be considered public.</p> <p> </p> <hr /> <h1><a name="return_values">RETURN VALUES</a></h1> <p><code>DH_generate_key()</code> returns 1 on success, 0 otherwise.</p> <p><code>DH_compute_key()</code> returns the size of the shared secret on success, -1 on error.</p> <p><code>DH_compute_key_padded()</code> returns <strong>DH_size(dh)</strong> on success, -1 on error.</p> <p>The error codes can be obtained by <em>ERR_get_error(3)</em>.</p> <p> </p> <hr /> <h1><a name="see_also">SEE ALSO</a></h1> <p><em>DH_new(3)</em>, <em>ERR_get_error(3)</em>, <em>RAND_bytes(3)</em>, <em>DH_size(3)</em></p> <p> </p> <hr /> <h1><a name="history">HISTORY</a></h1> <p><code>DH_compute_key_padded()</code> was added in OpenSSL 1.0.2.</p> <p> </p> <hr /> <h1><a name="copyright">COPYRIGHT</a></h1> <p>Copyright 2000-2021 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>