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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>EVP_PKEY_derive</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="#notes">NOTES</a></li> <li><a href="#return_values">RETURN VALUES</a></li> <li><a href="#examples">EXAMPLES</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>EVP_PKEY_derive_init, EVP_PKEY_derive_set_peer, EVP_PKEY_derive - derive public key algorithm shared secret</p> <p> </p> <hr /> <h1><a name="synopsis">SYNOPSIS</a></h1> <pre> #include <openssl/evp.h></pre> <pre> int EVP_PKEY_derive_init(EVP_PKEY_CTX *ctx); int EVP_PKEY_derive_set_peer(EVP_PKEY_CTX *ctx, EVP_PKEY *peer); int EVP_PKEY_derive(EVP_PKEY_CTX *ctx, unsigned char *key, size_t *keylen);</pre> <p> </p> <hr /> <h1><a name="description">DESCRIPTION</a></h1> <p>The <code>EVP_PKEY_derive_init()</code> function initializes a public key algorithm context using key <strong>pkey</strong> for shared secret derivation.</p> <p>The <code>EVP_PKEY_derive_set_peer()</code> function sets the peer key: this will normally be a public key.</p> <p>The <code>EVP_PKEY_derive()</code> derives a shared secret using <strong>ctx</strong>. If <strong>key</strong> is <strong>NULL</strong> then the maximum size of the output buffer is written to the <strong>keylen</strong> parameter. If <strong>key</strong> is not <strong>NULL</strong> then before the call the <strong>keylen</strong> parameter should contain the length of the <strong>key</strong> buffer, if the call is successful the shared secret is written to <strong>key</strong> and the amount of data written to <strong>keylen</strong>.</p> <p> </p> <hr /> <h1><a name="notes">NOTES</a></h1> <p>After the call to <code>EVP_PKEY_derive_init()</code> algorithm specific control operations can be performed to set any appropriate parameters for the operation.</p> <p>The function <code>EVP_PKEY_derive()</code> can be called more than once on the same context if several operations are performed using the same parameters.</p> <p> </p> <hr /> <h1><a name="return_values">RETURN VALUES</a></h1> <p><code>EVP_PKEY_derive_init()</code> and <code>EVP_PKEY_derive()</code> return 1 for success and 0 or a negative value for failure. In particular a return value of -2 indicates the operation is not supported by the public key algorithm.</p> <p> </p> <hr /> <h1><a name="examples">EXAMPLES</a></h1> <p>Derive shared secret (for example DH or EC keys):</p> <pre> #include <openssl/evp.h> #include <openssl/rsa.h></pre> <pre> EVP_PKEY_CTX *ctx; ENGINE *eng; unsigned char *skey; size_t skeylen; EVP_PKEY *pkey, *peerkey; /* NB: assumes pkey, eng, peerkey have been already set up */</pre> <pre> ctx = EVP_PKEY_CTX_new(pkey, eng); if (!ctx) /* Error occurred */ if (EVP_PKEY_derive_init(ctx) <= 0) /* Error */ if (EVP_PKEY_derive_set_peer(ctx, peerkey) <= 0) /* Error */</pre> <pre> /* Determine buffer length */ if (EVP_PKEY_derive(ctx, NULL, &skeylen) <= 0) /* Error */</pre> <pre> skey = OPENSSL_malloc(skeylen);</pre> <pre> if (!skey) /* malloc failure */</pre> <pre> if (EVP_PKEY_derive(ctx, skey, &skeylen) <= 0) /* Error */</pre> <pre> /* Shared secret is skey bytes written to buffer skey */</pre> <p> </p> <hr /> <h1><a name="see_also">SEE ALSO</a></h1> <p><em>EVP_PKEY_CTX_new(3)</em>, <em>EVP_PKEY_encrypt(3)</em>, <em>EVP_PKEY_decrypt(3)</em>, <em>EVP_PKEY_sign(3)</em>, <em>EVP_PKEY_verify(3)</em>, <em>EVP_PKEY_verify_recover(3)</em>,</p> <p> </p> <hr /> <h1><a name="history">HISTORY</a></h1> <p>These functions were added in OpenSSL 1.0.0.</p> <p> </p> <hr /> <h1><a name="copyright">COPYRIGHT</a></h1> <p>Copyright 2006-2019 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>