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EVP_PKEY_CTX_set_tls1_prf_md(3)     OpenSSL    EVP_PKEY_CTX_set_tls1_prf_md(3)



NAME
       EVP_PKEY_CTX_set_tls1_prf_md, EVP_PKEY_CTX_set1_tls1_prf_secret,
       EVP_PKEY_CTX_add1_tls1_prf_seed - TLS PRF key derivation algorithm

LIBRARY
       libcrypto, -lcrypto

SYNOPSIS
        #include <openssl/kdf.h>

        int EVP_PKEY_CTX_set_tls1_prf_md(EVP_PKEY_CTX *pctx, const EVP_MD *md);
        int EVP_PKEY_CTX_set1_tls1_prf_secret(EVP_PKEY_CTX *pctx,
                                              unsigned char *sec, int seclen);
        int EVP_PKEY_CTX_add1_tls1_prf_seed(EVP_PKEY_CTX *pctx,
                                            unsigned char *seed, int seedlen);

DESCRIPTION
       The EVP_PKEY_TLS1_PRF algorithm implements the PRF key derivation
       function for TLS. It has no associated private key and only implements
       key derivation using EVP_PKEY_derive(3).

       EVP_PKEY_set_tls1_prf_md() sets 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_PKEY_CTX_set_tls1_prf_secret() sets the secret value of the TLS PRF
       to seclen bytes of the buffer sec. Any existing secret value is
       replaced and any seed is reset.

       EVP_PKEY_CTX_add1_tls1_prf_seed() sets the seed to seedlen bytes of
       seed.  If a seed is already set it is appended to the existing value.

STRING CTRLS
       The TLS PRF also supports string based control operations using
       EVP_PKEY_CTX_ctrl_str(3).  The type parameter "md" uses the supplied
       value as the name of the digest algorithm to use.  The type parameters
       "secret" and "seed" use the supplied value parameter as a secret or
       seed value.  The names "hexsecret" and "hexseed" are similar except
       they take a hex string which is converted to binary.

NOTES
       A context for the TLS PRF can be obtained by calling:

        EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_TLS1_PRF, NULL);

       The digest, secret value and seed must be set before a key is derived
       or an error occurs.

       The total length of all seeds cannot exceed 1024 bytes in length: this
       should be more than enough for any normal use of the TLS PRF.

       The output length of the PRF is specified by the length parameter in
       the EVP_PKEY_derive() function. Since the output length is variable,
       setting the buffer to NULL is not meaningful for the TLS PRF.

       Optimised versions of the TLS PRF can be implemented in an ENGINE.

RETURN VALUES
       All these functions 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.

EXAMPLES
       This example derives 10 bytes using SHA-256 with the secret key
       "secret" and seed value "seed":

        EVP_PKEY_CTX *pctx;
        unsigned char out[10];
        size_t outlen = sizeof(out);

        pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_TLS1_PRF, NULL);
        if (EVP_PKEY_derive_init(pctx) <= 0)
            /* Error */
        if (EVP_PKEY_CTX_set_tls1_prf_md(pctx, EVP_sha256()) <= 0)
            /* Error */
        if (EVP_PKEY_CTX_set1_tls1_prf_secret(pctx, "secret", 6) <= 0)
            /* Error */
        if (EVP_PKEY_CTX_add1_tls1_prf_seed(pctx, "seed", 4) <= 0)
            /* Error */
        if (EVP_PKEY_derive(pctx, out, &outlen) <= 0)
            /* Error */

SEE ALSO
       EVP_PKEY_CTX_new(3), EVP_PKEY_CTX_ctrl_str(3), EVP_PKEY_derive(3)

HISTORY
       All of the functions described here were converted from macros to
       functions in OpenSSL 3.0.

COPYRIGHT
       Copyright 2016-2020 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>.



3.0.12                            2023-05-07   EVP_PKEY_CTX_set_tls1_prf_md(3)