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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" EVP_KDF\-TLS1_PRF \- The TLS1 PRF EVP_KDF implementation .SH "DESCRIPTION" .IX Header "DESCRIPTION" Support for computing the \fB\s-1TLS1\s0\fR \s-1PRF\s0 through the \fB\s-1EVP_KDF\s0\fR \s-1API.\s0 .PP 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 .SS "Identity" .IX Subsection "Identity" \&\*(L"\s-1TLS1\-PRF\*(R"\s0 is the name for this implementation; it can be used with the \fIEVP_KDF_fetch()\fR function. .SS "Supported parameters" .IX Subsection "Supported parameters" The supported parameters are: .ie n .IP """properties"" (\fB\s-1OSSL_KDF_PARAM_PROPERTIES\s0\fR) <\s-1UTF8\s0 string>" 4 .el .IP "``properties'' (\fB\s-1OSSL_KDF_PARAM_PROPERTIES\s0\fR) <\s-1UTF8\s0 string>" 4 .IX Item "properties (OSSL_KDF_PARAM_PROPERTIES) " .PD 0 .ie n .IP """digest"" (\fB\s-1OSSL_KDF_PARAM_DIGEST\s0\fR) <\s-1UTF8\s0 string>" 4 .el .IP "``digest'' (\fB\s-1OSSL_KDF_PARAM_DIGEST\s0\fR) <\s-1UTF8\s0 string>" 4 .IX Item "digest (OSSL_KDF_PARAM_DIGEST) " .PD These parameters work as described in \*(L"\s-1PARAMETERS\*(R"\s0 in \s-1\fIEVP_KDF\s0\fR\|(3). .Sp The \fB\s-1OSSL_KDF_PARAM_DIGEST\s0\fR parameter is used to set the message digest associated with the \s-1TLS PRF.\s0 \&\fIEVP_md5_sha1()\fR is treated as a special case which uses the \&\s-1PRF\s0 algorithm using both \fB\s-1MD5\s0\fR and \fB\s-1SHA1\s0\fR as used in \s-1TLS 1.0\s0 and 1.1. .ie n .IP """secret"" (\fB\s-1OSSL_KDF_PARAM_SECRET\s0\fR) " 4 .el .IP "``secret'' (\fB\s-1OSSL_KDF_PARAM_SECRET\s0\fR) " 4 .IX Item "secret (OSSL_KDF_PARAM_SECRET) " This parameter sets the secret value of the \s-1TLS PRF.\s0 Any existing secret value is replaced. .ie n .IP """seed"" (\fB\s-1OSSL_KDF_PARAM_SEED\s0\fR) " 4 .el .IP "``seed'' (\fB\s-1OSSL_KDF_PARAM_SEED\s0\fR) " 4 .IX Item "seed (OSSL_KDF_PARAM_SEED) " 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 .SH "NOTES" .IX Header "NOTES" A context for the \s-1TLS PRF\s0 can be obtained by calling: .PP .Vb 2 \& EVP_KDF *kdf = EVP_KDF_fetch(NULL, "TLS1\-PRF", NULL); \& EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf); .Ve .PP The digest, secret value and seed must be set before a key is derived otherwise an error will occur. .PP The output length of the \s-1PRF\s0 is specified by the \fIkeylen\fR parameter to the \&\fIEVP_KDF_derive()\fR function. .SH "EXAMPLES" .IX 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": .PP .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 .SH "CONFORMING TO" .IX Header "CONFORMING TO" \&\s-1RFC 2246, RFC 5246\s0 and \s-1NIST SP 800\-135\s0 r1 .SH "SEE ALSO" .IX Header "SEE ALSO" \&\s-1\fIEVP_KDF\s0\fR\|(3), \&\fIEVP_KDF_CTX_new\fR\|(3), \&\fIEVP_KDF_CTX_free\fR\|(3), \&\fIEVP_KDF_CTX_set_params\fR\|(3), \&\fIEVP_KDF_derive\fR\|(3), \&\*(L"\s-1PARAMETERS\*(R"\s0 in \s-1\fIEVP_KDF\s0\fR\|(3) .SH "HISTORY" .IX Header "HISTORY" This functionality was added in OpenSSL 3.0. .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2018\-2021 The OpenSSL Project Authors. All Rights Reserved. .PP 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 .