1EVP_KDF-TLS1_PRF(7ossl)             OpenSSL            EVP_KDF-TLS1_PRF(7ossl)
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NAME

6       EVP_KDF-TLS1_PRF - The TLS1 PRF EVP_KDF implementation
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DESCRIPTION

9       Support for computing the TLS1 PRF through the EVP_KDF API.
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11       The EVP_KDF-TLS1_PRF algorithm implements the PRF used by TLS versions
12       up to and including TLS 1.2.
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14   Identity
15       "TLS1-PRF" is the name for this implementation; it can be used with the
16       EVP_KDF_fetch() function.
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18   Supported parameters
19       The supported parameters are:
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21       "properties" (OSSL_KDF_PARAM_PROPERTIES) <UTF8 string>
22       "digest" (OSSL_KDF_PARAM_DIGEST) <UTF8 string>
23           These parameters work as described in "PARAMETERS" in EVP_KDF(3).
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25           The OSSL_KDF_PARAM_DIGEST parameter is used to set the message
26           digest associated with the TLS PRF.  EVP_md5_sha1() is treated as a
27           special case which uses the PRF algorithm using both MD5 and SHA1
28           as used in TLS 1.0 and 1.1.
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30       "secret" (OSSL_KDF_PARAM_SECRET) <octet string>
31           This parameter sets the secret value of the TLS PRF.  Any existing
32           secret value is replaced.
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34       "seed" (OSSL_KDF_PARAM_SEED) <octet string>
35           This parameter sets the context seed.  The length of the context
36           seed cannot exceed 1024 bytes; this should be more than enough for
37           any normal use of the TLS PRF.
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NOTES

40       A context for the TLS PRF can be obtained by calling:
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42        EVP_KDF *kdf = EVP_KDF_fetch(NULL, "TLS1-PRF", NULL);
43        EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
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45       The digest, secret value and seed must be set before a key is derived
46       otherwise an error will occur.
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48       The output length of the PRF is specified by the keylen parameter to
49       the EVP_KDF_derive() function.
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EXAMPLES

52       This example derives 10 bytes using SHA-256 with the secret key
53       "secret" and seed value "seed":
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55        EVP_KDF *kdf;
56        EVP_KDF_CTX *kctx;
57        unsigned char out[10];
58        OSSL_PARAM params[4], *p = params;
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60        kdf = EVP_KDF_fetch(NULL, "TLS1-PRF", NULL);
61        kctx = EVP_KDF_CTX_new(kdf);
62        EVP_KDF_free(kdf);
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64        *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
65                                                SN_sha256, strlen(SN_sha256));
66        *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SECRET,
67                                                 "secret", (size_t)6);
68        *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SEED,
69                                                 "seed", (size_t)4);
70        *p = OSSL_PARAM_construct_end();
71        if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) {
72            error("EVP_KDF_derive");
73        }
74        EVP_KDF_CTX_free(kctx);
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CONFORMING TO

77       RFC 2246, RFC 5246 and NIST SP 800-135 r1
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SEE ALSO

80       EVP_KDF(3), EVP_KDF_CTX_new(3), EVP_KDF_CTX_free(3),
81       EVP_KDF_CTX_set_params(3), EVP_KDF_derive(3), "PARAMETERS" in
82       EVP_KDF(3)
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HISTORY

85       This functionality was added in OpenSSL 3.0.
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88       Copyright 2018-2022 The OpenSSL Project Authors. All Rights Reserved.
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90       Licensed under the Apache License 2.0 (the "License").  You may not use
91       this file except in compliance with the License.  You can obtain a copy
92       in the file LICENSE in the source distribution or at
93       <https://www.openssl.org/source/license.html>.
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973.1.1                             2023-08-31           EVP_KDF-TLS1_PRF(7ossl)
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