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Title "EVP_KDF-TLS1_PRF 7ossl" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
EVP_KDF-TLS1_PRF - The TLS1 PRF EVP_KDF implementation Header "DESCRIPTION" Support for computing the \s-1TLS1\s0 \s-1PRF\s0 through the \s-1EVP_KDF\s0 \s-1API.\s0

The \s-1EVP_KDF-TLS1_PRF\s0 algorithm implements the \s-1PRF\s0 used by \s-1TLS\s0 versions up to and including \s-1TLS 1.2.\s0

Subsection "Identity" \*(L"\s-1TLS1-PRF\*(R"\s0 is the name for this implementation; it can be used with the EVP_KDF_fetch() function. Subsection "Supported parameters" The supported parameters are: Item "properties (OSSL_KDF_PARAM_PROPERTIES) <UTF8 string>"

0 Item "digest (OSSL_KDF_PARAM_DIGEST) <UTF8 string>"

These parameters work as described in \*(L"\s-1PARAMETERS\*(R"\s0 in \s-1EVP_KDF\s0\|(3). .Sp The \s-1OSSL_KDF_PARAM_DIGEST\s0 parameter is used to set the message digest associated with the \s-1TLS PRF.\s0 \fBEVP_md5_sha1() is treated as a special case which uses the \s-1PRF\s0 algorithm using both \s-1MD5\s0 and \s-1SHA1\s0 as used in \s-1TLS 1.0\s0 and 1.1. Item "secret (OSSL_KDF_PARAM_SECRET) <octet string>" This parameter sets the secret value of the \s-1TLS PRF.\s0 Any existing secret value is replaced. Item "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 \s-1TLS PRF.\s0

Header "NOTES" A context for the \s-1TLS PRF\s0 can be obtained by calling:

.Vb 2 EVP_KDF *kdf = EVP_KDF_fetch(NULL, "TLS1-PRF", NULL); EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf); .Ve

The digest, secret value and seed must be set before a key is derived otherwise an error will occur.

The output length of the \s-1PRF\s0 is specified by the keylen parameter to the \fBEVP_KDF_derive() function.

Header "EXAMPLES" This example derives 10 bytes using \s-1SHA-256\s0 with the secret key \*(L"secret\*(R" and seed value \*(L"seed\*(R":

.Vb 4 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); .Ve

Header "CONFORMING TO" \s-1RFC 2246, RFC 5246\s0 and \s-1NIST SP 800-135\s0 r1 Header "SEE ALSO" \s-1EVP_KDF\s0\|(3), \fBEVP_KDF_CTX_new\|(3), \fBEVP_KDF_CTX_free\|(3), \fBEVP_KDF_CTX_set_params\|(3), \fBEVP_KDF_derive\|(3), \*(L"\s-1PARAMETERS\*(R"\s0 in \s-1EVP_KDF\s0\|(3) Header "HISTORY" This functionality was added in OpenSSL 3.0. Header "COPYRIGHT" Copyright 2018-2021 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.