# EVP_KDF-TLS1_PRF(7SSL) - man - phpMan

[EVP_KDF-TLS1_PRF(7SSL)](https://www.chedong.com/phpMan.php/man/EVPKDF-TLS1PRF/7SSL/markdown)                         OpenSSL                        [EVP_KDF-TLS1_PRF(7SSL)](https://www.chedong.com/phpMan.php/man/EVPKDF-TLS1PRF/7SSL/markdown)



## 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.

### Identity
       "TLS1-PRF" is the name for this implementation; it can be used with the **EVP**___**KDF**___**fetch()**
       function.

### Supported parameters
       The supported parameters are:

       "properties" (**OSSL**___**KDF**___**PARAM**___**PROPERTIES**) <UTF8 string>
       "digest" (**OSSL**___**KDF**___**PARAM**___**DIGEST**) <UTF8 string>
           These parameters work as described in "PARAMETERS" in **EVP**___**[KDF**(3)](https://www.chedong.com/phpMan.php/man/KDF/3/markdown).

           The **OSSL**___**KDF**___**PARAM**___**DIGEST** parameter 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.

       "secret" (**OSSL**___**KDF**___**PARAM**___**SECRET**) <octet string>
           This parameter sets the secret value of the TLS PRF.  Any existing secret value is
           replaced.

       "seed" (**OSSL**___**KDF**___**PARAM**___**SEED**) <octet string>
           This parameter sets the context seed.  The length of the context seed cannot exceed 1024
           bytes; this should be more than enough for any normal use of the TLS PRF.

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

        EVP_KDF *kdf = EVP_KDF_fetch(NULL, "TLS1-PRF", NULL);
        EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);

       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.

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

        EVP_KDF *kdf;
        EVP_KDF_CTX *kctx;
        unsigned char out[10];
        OSSL_PARAM params[4], *p = params;

        kdf = EVP_KDF_fetch(NULL, "TLS1-PRF", NULL);
        kctx = EVP_KDF_CTX_new(kdf);
        EVP_KDF_free(kdf);

        *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,
                                                 "secret", (size_t)6);
        *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SEED,
                                                 "seed", (size_t)4);
        *p = OSSL_PARAM_construct_end();
        if (EVP_KDF_derive(kctx, out, [sizeof(out)](https://www.chedong.com/phpMan.php/man/sizeof/out/markdown), params) <= 0) {
            error("EVP_KDF_derive");
        }
        EVP_KDF_CTX_free(kctx);

## CONFORMING TO
       RFC 2246, RFC 5246 and NIST SP 800-135 r1

## SEE ALSO
       **EVP**___**[KDF**(3)](https://www.chedong.com/phpMan.php/man/KDF/3/markdown), **EVP**___**KDF**___**CTX**___**[new**(3)](https://www.chedong.com/phpMan.php/man/new/3/markdown), **EVP**___**KDF**___**CTX**___**[free**(3)](https://www.chedong.com/phpMan.php/man/free/3/markdown), **EVP**___**KDF**___**CTX**___**set**___**[params**(3)](https://www.chedong.com/phpMan.php/man/params/3/markdown),
       **EVP**___**KDF**___**[derive**(3)](https://www.chedong.com/phpMan.php/man/derive/3/markdown), "PARAMETERS" in **EVP**___**[KDF**(3)](https://www.chedong.com/phpMan.php/man/KDF/3/markdown)

## COPYRIGHT
       Copyright 2018-2021 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>>.



3.0.2                                        2026-04-07                       [EVP_KDF-TLS1_PRF(7SSL)](https://www.chedong.com/phpMan.php/man/EVPKDF-TLS1PRF/7SSL/markdown)