info > EVP_KDF-TLS1_PRF(7)

man perldoc info pydoc3 ri search

📛 NAME

EVP_KDF-TLS1_PRF - The TLS1 PRF EVP_KDF implementation

🚀 Quick Reference

Use Case	Command / Code Snippet	Description
🔐 Derive TLS 1.2 PRF key (SHA-256)	EVP_KDF_derive(kctx, out, 10, params)	Derive 10 bytes using SHA-256 with secret "secret" and seed "seed"
🔁 Derive TLS 1.0/1.1 PRF key (MD5+SHA1)	EVP_KDF_fetch(NULL, "TLS1-PRF", NULL) + digest = EVP_md5_sha1()	Use the combined MD5+SHA1 PRF as specified in TLS 1.0 and 1.1
⚙️ Fetch the KDF implementation	EVP_KDF *kdf = EVP_KDF_fetch(NULL, "TLS1-PRF", NULL);	Obtain a context for TLS1-PRF derivation

📖 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

• 🔧 "properties" (OSSL_KDF_PARAM_PROPERTIES) <UTF8 string>
• 🔧 "digest" (OSSL_KDF_PARAM_DIGEST) <UTF8 string> — These parameters work as described in EVP_KDF(3). The OSSL_KDF_PARAM_DIGEST parameter 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.
• 🔑 "secret" (OSSL_KDF_PARAM_SECRET) <octet string> — Sets the secret value of the TLS PRF. Any existing secret value is replaced.
• 🌱 "seed" (OSSL_KDF_PARAM_SEED) <octet string> — 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), 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), EVP_KDF_CTX_new(3), EVP_KDF_CTX_free(3), EVP_KDF_CTX_set_params(3), EVP_KDF_derive(3), "PARAMETERS" in EVP_KDF(3)

© 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 2026-06-02 EVP_KDF-TLS1_PRF(7SSL)

📛 NAME 🚀 Quick Reference 📖 DESCRIPTION 📝 NOTES 💻 EXAMPLES 📜 CONFORMING TO 🔗 SEE ALSO © COPYRIGHT