205 lines
7.6 KiB
HTML
Executable File
205 lines
7.6 KiB
HTML
Executable File
<?xml version="1.0" ?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<title>EVP_KDF-SSHKDF</title>
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<meta http-equiv="content-type" content="text/html; charset=utf-8" />
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<link rev="made" href="mailto:root@localhost" />
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</head>
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<body style="background-color: white">
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<!-- INDEX BEGIN -->
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<div name="index">
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<p><a name="__index__"></a></p>
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<ul>
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<li><a href="#name">NAME</a></li>
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<li><a href="#description">DESCRIPTION</a></li>
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<ul>
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<li><a href="#identity">Identity</a></li>
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<li><a href="#supported_parameters">Supported parameters</a></li>
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</ul>
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<li><a href="#notes">NOTES</a></li>
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<li><a href="#examples">EXAMPLES</a></li>
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<li><a href="#conforming_to">CONFORMING TO</a></li>
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<li><a href="#see_also">SEE ALSO</a></li>
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<li><a href="#copyright">COPYRIGHT</a></li>
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</ul>
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<hr name="index" />
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</div>
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<!-- INDEX END -->
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<p>
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</p>
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<hr />
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<h1><a name="name">NAME</a></h1>
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<p>EVP_KDF-SSHKDF - The SSHKDF EVP_KDF implementation</p>
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<p>
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</p>
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<hr />
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<h1><a name="description">DESCRIPTION</a></h1>
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<p>Support for computing the <strong>SSHKDF</strong> KDF through the <strong>EVP_KDF</strong> API.</p>
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<p>The EVP_KDF-SSHKDF algorithm implements the SSHKDF key derivation function.
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It is defined in <a href="http://www.ietf.org/rfc/rfc4253.txt" class="rfc">RFC 4253</a>, section 7.2 and is used by SSH to derive IVs,
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encryption keys and integrity keys.
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Five inputs are required to perform key derivation: The hashing function
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(for example SHA256), the Initial Key, the Exchange Hash, the Session ID,
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and the derivation key type.</p>
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<p>
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</p>
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<h2><a name="identity">Identity</a></h2>
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<p>"SSHKDF" is the name for this implementation; it
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can be used with the <code>EVP_KDF_fetch()</code> function.</p>
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<p>
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</p>
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<h2><a name="supported_parameters">Supported parameters</a></h2>
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<p>The supported parameters are:</p>
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<dl>
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<dt><strong><a name="properties_ossl_kdf_param_properties_utf8_string" class="item">"properties" (<strong>OSSL_KDF_PARAM_PROPERTIES</strong>) <UTF8 string></a></strong></dt>
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<dt><strong><a name="digest_ossl_kdf_param_digest_utf8_string" class="item">"digest" (<strong>OSSL_KDF_PARAM_DIGEST</strong>) <UTF8 string></a></strong></dt>
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<dt><strong><a name="key_ossl_kdf_param_key_octet_string" class="item">"key" (<strong>OSSL_KDF_PARAM_KEY</strong>) <octet string></a></strong></dt>
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<dd>
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<p>These parameters work as described in <em>EVP_KDF(3)/PARAMETERS</em>.</p>
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</dd>
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<dt><strong><a name="xcghash_ossl_kdf_param_sshkdf_xcghash_octet_string" class="item">"xcghash" (<strong>OSSL_KDF_PARAM_SSHKDF_XCGHASH</strong>) <octet string></a></strong></dt>
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<dt><strong><a name="session_id_ossl_kdf_param_sshkdf_session_id_octet_string" class="item">"session_id" (<strong>OSSL_KDF_PARAM_SSHKDF_SESSION_ID</strong>) <octet string></a></strong></dt>
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<dd>
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<p>These parameters set the respective values for the KDF.
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If a value is already set, the contents are replaced.</p>
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</dd>
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<dt><strong><a name="type_ossl_kdf_param_sshkdf_type_integer" class="item">"type" (<strong>OSSL_KDF_PARAM_SSHKDF_TYPE</strong>) <integer></a></strong></dt>
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<dd>
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<p>This parameter sets the type for the SSHHKDF operation.
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There are six supported types:</p>
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<dl>
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<dt><strong><a name="evp_kdf_sshkdf_type_initial_iv_cli_to_srv" class="item">EVP_KDF_SSHKDF_TYPE_INITIAL_IV_CLI_TO_SRV</a></strong></dt>
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<dd>
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<p>The Initial IV from client to server.
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A single char of value 65 (ASCII char 'A').</p>
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</dd>
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<dt><strong><a name="evp_kdf_sshkdf_type_initial_iv_srv_to_cli" class="item">EVP_KDF_SSHKDF_TYPE_INITIAL_IV_SRV_TO_CLI</a></strong></dt>
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<dd>
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<p>The Initial IV from server to client
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A single char of value 66 (ASCII char 'B').</p>
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</dd>
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<dt><strong><a name="evp_kdf_sshkdf_type_encryption_key_cli_to_srv" class="item">EVP_KDF_SSHKDF_TYPE_ENCRYPTION_KEY_CLI_TO_SRV</a></strong></dt>
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<dd>
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<p>The Encryption Key from client to server
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A single char of value 67 (ASCII char 'C').</p>
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</dd>
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<dt><strong><a name="evp_kdf_sshkdf_type_encryption_key_srv_to_cli" class="item">EVP_KDF_SSHKDF_TYPE_ENCRYPTION_KEY_SRV_TO_CLI</a></strong></dt>
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<dd>
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<p>The Encryption Key from server to client
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A single char of value 68 (ASCII char 'D').</p>
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</dd>
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<dt><strong><a name="evp_kdf_sshkdf_type_integrity_key_cli_to_srv" class="item">EVP_KDF_SSHKDF_TYPE_INTEGRITY_KEY_CLI_TO_SRV</a></strong></dt>
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<dd>
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<p>The Integrity Key from client to server
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A single char of value 69 (ASCII char 'E').</p>
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</dd>
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<dt><strong><a name="evp_kdf_sshkdf_type_integrity_key_srv_to_cli" class="item">EVP_KDF_SSHKDF_TYPE_INTEGRITY_KEY_SRV_TO_CLI</a></strong></dt>
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<dd>
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<p>The Integrity Key from client to server
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A single char of value 70 (ASCII char 'F').</p>
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</dd>
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</dl>
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</dd>
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</dl>
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<p>
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</p>
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<hr />
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<h1><a name="notes">NOTES</a></h1>
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<p>A context for SSHKDF can be obtained by calling:</p>
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<pre>
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EVP_KDF *kdf = EVP_KDF_fetch(NULL, "SSHKDF", NULL);
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EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);</pre>
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<p>The output length of the SSHKDF derivation is specified via the <em>keylen</em>
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parameter to the <em>EVP_KDF_derive(3)</em> function.
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Since the SSHKDF output length is variable, calling <em>EVP_KDF_size(3)</em>
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to obtain the requisite length is not meaningful. The caller must
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allocate a buffer of the desired length, and pass that buffer to the
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<em>EVP_KDF_derive(3)</em> function along with the desired length.</p>
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<p>
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</p>
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<hr />
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<h1><a name="examples">EXAMPLES</a></h1>
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<p>This example derives an 8 byte IV using SHA-256 with a 1K "key" and appropriate
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"xcghash" and "session_id" values:</p>
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<pre>
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EVP_KDF *kdf;
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EVP_KDF_CTX *kctx;
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unsigned char key[1024] = "01234...";
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unsigned char xcghash[32] = "012345...";
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unsigned char session_id[32] = "012345...";
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unsigned char out[8];
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size_t outlen = sizeof(out);
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OSSL_PARAM params[6], *p = params;</pre>
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<pre>
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kdf = EVP_KDF_fetch(NULL, "SSHKDF", NULL);
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kctx = EVP_KDF_CTX_new(kdf);
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EVP_KDF_free(kdf);</pre>
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<pre>
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*p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
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SN_sha256, strlen(SN_sha256));
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY,
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key, (size_t)1024);
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SSHKDF_XCGHASH,
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xcghash, (size_t)32);
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
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session_id, (size_t)32);
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*p++ = OSSL_PARAM_construct_int(OSSL_KDF_PARAM_SSHKDF_TYPE,
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EVP_KDF_SSHKDF_TYPE_INITIAL_IV_CLI_TO_SRV);
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*p = OSSL_PARAM_construct_end();
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if (EVP_KDF_CTX_set_params(kctx, params) <= 0)
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/* Error */</pre>
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<pre>
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if (EVP_KDF_derive(kctx, out, &outlen) <= 0)
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/* Error */</pre>
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<p>
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</p>
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<hr />
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<h1><a name="conforming_to">CONFORMING TO</a></h1>
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<p>RFC 4253</p>
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<p>
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</p>
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<hr />
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<h1><a name="see_also">SEE ALSO</a></h1>
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<p><em>EVP_KDF(3)</em>,
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<em>EVP_KDF_CTX_new(3)</em>,
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<em>EVP_KDF_CTX_free(3)</em>,
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<em>EVP_KDF_CTX_set_params(3)</em>,
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<em>EVP_KDF_size(3)</em>,
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<em>EVP_KDF_derive(3)</em>,
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<em>EVP_KDF(3)/PARAMETERS</em></p>
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<p>
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</p>
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<hr />
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<h1><a name="copyright">COPYRIGHT</a></h1>
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<p>Copyright 2016-2019 The OpenSSL Project Authors. All Rights Reserved.</p>
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<p>Licensed under the OpenSSL license (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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<a href="https://www.openssl.org/source/license.html">https://www.openssl.org/source/license.html</a>.</p>
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</body>
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</html>
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