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_CTX_set_params(kctx, params) <= 0) {
     error("EVP_KDF_CTX_set_params");
 }
 if (EVP_KDF_derive(kctx, out, sizeof(out)) <= 0) {
     error("EVP_KDF_derive");
 }
 EVP_KDF_CTX_free(kctx);

CONFORMING TO

RFC 2246, RFC 5246 and NIST SP 800-135 r1

SEE ALSO