openssl-prebuild/linux_amd64/share/doc/openssl/html/man7/EVP_KDF-X963.html
2020-03-02 16:50:34 +00:00

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<title>EVP_KDF-X963</title>
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<p><a name="__index__"></a></p>
<ul>
<li><a href="#name">NAME</a></li>
<li><a href="#description">DESCRIPTION</a></li>
<ul>
<li><a href="#identity">Identity</a></li>
<li><a href="#supported_parameters">Supported parameters</a></li>
</ul>
<li><a href="#notes">NOTES</a></li>
<li><a href="#examples">EXAMPLES</a></li>
<li><a href="#conforming_to">CONFORMING TO</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>
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<h1><a name="name">NAME</a></h1>
<p>EVP_KDF-X963 - The X9.63-2001 EVP_KDF implementation</p>
<p>
</p>
<hr />
<h1><a name="description">DESCRIPTION</a></h1>
<p>The EVP_KDF-X963 algorithm implements the key derivation function (X963KDF).
X963KDF is used by Cryptographic Message Syntax (CMS) for EC KeyAgreement, to
derive a key using input such as a shared secret key and shared info.</p>
<p>
</p>
<h2><a name="identity">Identity</a></h2>
<p>&quot;X963KDF&quot; is the name for this implementation; it
can be used with the <code>EVP_KDF_fetch()</code> function.</p>
<p>
</p>
<h2><a name="supported_parameters">Supported parameters</a></h2>
<p>The supported parameters are:</p>
<dl>
<dt><strong><a name="properties_ossl_kdf_param_properties_utf8_string" class="item">&quot;properties&quot; (<strong>OSSL_KDF_PARAM_PROPERTIES</strong>) &lt;UTF8 string&gt;</a></strong></dt>
<dt><strong><a name="digest_ossl_kdf_param_digest_utf8_string" class="item">&quot;digest&quot; (<strong>OSSL_KDF_PARAM_DIGEST</strong>) &lt;UTF8 string&gt;</a></strong></dt>
<dd>
<p>These parameters work as described in <em>EVP_KDF(3)/PARAMETERS</em>.</p>
</dd>
<dt><strong><a name="key_ossl_kdf_param_key_octet_string" class="item">&quot;key&quot; (<strong>OSSL_KDF_PARAM_KEY</strong>) &lt;octet string&gt;</a></strong></dt>
<dd>
<p>The shared secret used for key derivation.
This parameter sets the secret.</p>
</dd>
<dt><strong><a name="info_ossl_kdf_param_info_octet_string" class="item">&quot;info&quot; (<strong>OSSL_KDF_PARAM_INFO</strong>) &lt;octet string&gt;</a></strong></dt>
<dd>
<p>This parameter specifies an optional value for shared info.</p>
</dd>
</dl>
<p>
</p>
<hr />
<h1><a name="notes">NOTES</a></h1>
<p>X963KDF is very similar to the SSKDF that uses a digest as the auxiliary function,
X963KDF appends the counter to the secret, whereas SSKDF prepends the counter.</p>
<p>A context for X963KDF can be obtained by calling:</p>
<pre>
EVP_KDF *kdf = EVP_KDF_fetch(NULL, &quot;X963KDF&quot;, NULL);
EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);</pre>
<p>The output length of an X963KDF is specified via the <em>keylen</em>
parameter to the <em>EVP_KDF_derive(3)</em> function.</p>
<p>
</p>
<hr />
<h1><a name="examples">EXAMPLES</a></h1>
<p>This example derives 10 bytes, with the secret key &quot;secret&quot; and sharedinfo
value &quot;label&quot;:</p>
<pre>
EVP_KDF *kdf;
EVP_KDF_CTX *kctx;
unsigned char out[10];
OSSL_PARAM params[4], *p = params;</pre>
<pre>
kdf = EVP_KDF_fetch(NULL, &quot;X963KDF&quot;, NULL);
kctx = EVP_KDF_CTX_new(kdf);
EVP_KDF_free(kdf);</pre>
<pre>
*p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
SN_sha256, strlen(SN_sha256));
*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SECRET,
&quot;secret&quot;, (size_t)6);
*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
&quot;label&quot;, (size_t)5);
*p = OSSL_PARAM_construct_end();
if (EVP_KDF_CTX_set_params(kctx, params) &lt;= 0) {
error(&quot;EVP_KDF_CTX_set_params&quot;);
}
if (EVP_KDF_derive(kctx, out, sizeof(out)) &lt;= 0) {
error(&quot;EVP_KDF_derive&quot;);
}</pre>
<pre>
EVP_KDF_CTX_free(kctx);</pre>
<p>
</p>
<hr />
<h1><a name="conforming_to">CONFORMING TO</a></h1>
<p>&quot;SEC 1: Elliptic Curve Cryptography&quot;</p>
<p>
</p>
<hr />
<h1><a name="see_also">SEE ALSO</a></h1>
<p><em>EVP_KDF(3)</em>,
<em>EVP_KDF_CTX_new(3)</em>,
<em>EVP_KDF_CTX_free(3)</em>,
<em>EVP_KDF_CTX_set_params(3)</em>,
<em>EVP_KDF_size(3)</em>,
<em>EVP_KDF_derive(3)</em>,
<em>EVP_KDF(3)/PARAMETERS</em></p>
<p>
</p>
<hr />
<h1><a name="history">HISTORY</a></h1>
<p>This functionality was added to OpenSSL 3.0.</p>
<p>
</p>
<hr />
<h1><a name="copyright">COPYRIGHT</a></h1>
<p>Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.</p>
<p>Licensed under the Apache License 2.0 (the &quot;License&quot;). 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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