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EVP_KDF_TLS1_PRF(7)                 OpenSSL                EVP_KDF_TLS1_PRF(7)
NAME
       EVP_KDF_TLS1_PRF - The TLS1 PRF EVP_KDF implementation
DESCRIPTION
       Support for computing the TLS1 PRF through the EVP_KDF API.
       The EVP_KDF_TLS1_PRF algorithm implements the PRF used by TLS versions
       up to and including TLS 1.2.
   Numeric identity
       EVP_KDF_TLS1_PRF is the numeric identity for this implementation; it
       can be used with the EVP_KDF_CTX_new_id() function.
   Supported controls
       The supported controls are:
       EVP_KDF_CTRL_SET_MD
           This control works as described in "CONTROLS" in EVP_KDF_CTX(3).
           The "EVP_KDF_CTRL_SET_MD" control is used to set the message digest
           associated with the TLS PRF.  EVP_md5_sha1() is treated as a
           special case which uses the PRF algorithm using both MD5 and SHA1
           as used in TLS 1.0 and 1.1.
       EVP_KDF_CTRL_SET_TLS_SECRET
           This control expects two arguments: "unsigned char *sec", "size_t
           seclen"
           Sets the secret value of the TLS PRF to seclen bytes of the buffer
           sec.  Any existing secret value is replaced.
           EVP_KDF_ctrl_str() takes two type strings for this control:
           "secret"
               The value string is used as is.
           "hexsecret"
               The value string is expected to be a hexadecimal number, which
               will be decoded before being passed on as the control value.
       EVP_KDF_CTRL_RESET_TLS_SEED
           This control does not expect any arguments.
           Resets the context seed buffer to zero length.
       EVP_KDF_CTRL_ADD_TLS_SEED
           This control expects two arguments: "unsigned char *seed", "size_t
           seedlen"
           Sets the seed to seedlen bytes of seed.  If a seed is already set
           it is appended to the existing value.
           The total length of the context seed buffer cannot exceed 1024
           bytes; this should be more than enough for any normal use of the
           TLS PRF.
           EVP_KDF_ctrl_str() takes two type strings for this control:
           "seed"
               The value string is used as is.
           "hexseed"
               The value string is expected to be a hexadecimal number, which
               will be decoded before being passed on as the control value.
NOTES
       A context for the TLS PRF can be obtained by calling:
        EVP_KDF_CTX *kctx = EVP_KDF_CTX_new_id(EVP_KDF_TLS1_PRF, NULL);
       The digest, secret value and seed must be set before a key is derived
       otherwise an error will occur.
       The output length of the PRF is specified by the "keylen" parameter to
       the EVP_KDF_derive() function.
EXAMPLE
       This example derives 10 bytes using SHA-256 with the secret key
       "secret" and seed value "seed":
        EVP_KDF_CTX *kctx;
        unsigned char out[10];
        kctx = EVP_KDF_CTX_new_id(EVP_KDF_TLS1_PRF);
        if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_MD, EVP_sha256()) <= 0) {
            error("EVP_KDF_CTRL_SET_MD");
        }
        if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_TLS_SECRET,
                         "secret", (size_t)6) <= 0) {
            error("EVP_KDF_CTRL_SET_TLS_SECRET");
        }
        if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_ADD_TLS_SEED, "seed", (size_t)4) <= 0) {
            error("EVP_KDF_CTRL_ADD_TLS_SEED");
        }
        if (EVP_KDF_derive(kctx, out, sizeof(out)) <= 0) {
            error("EVP_KDF_derive");
        }
        EVP_KDF_CTX_free(kctx);
SEE ALSO
       EVP_KDF_CTX, EVP_KDF_CTX_new_id(3), EVP_KDF_CTX_free(3),
       EVP_KDF_ctrl(3), EVP_KDF_derive(3), "CONTROLS" in EVP_KDF_CTX(3)
COPYRIGHT
       Copyright 2018 The OpenSSL Project Authors. All Rights Reserved.
       Licensed under the Apache License 2.0 (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
       <https://www.openssl.org/source/license.html>;.
1.1.1k                            2024-10-09               EVP_KDF_TLS1_PRF(7)