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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\-SS \- The Single Step / One Step EVP_KDF implementation .SH "DESCRIPTION" .IX Header "DESCRIPTION" The \s-1EVP_KDF\-SS\s0 algorithm implements the Single Step key derivation function (\s-1SSKDF\s0). \&\s-1SSKDF\s0 derives a key using input such as a shared secret key (that was generated during the execution of a key establishment scheme) and fixedinfo. \&\s-1SSKDF\s0 is also informally referred to as 'Concat \s-1KDF\s0'. .SS "Auxiliary function" .IX Subsection "Auxiliary function" The implementation uses a selectable auxiliary function H, which can be one of: .IP "\fBH(x) = hash(x, digest=md)\fR" 4 .IX Item "H(x) = hash(x, digest=md)" .PD 0 .IP "\fBH(x) = HMAC_hash(x, key=salt, digest=md)\fR" 4 .IX Item "H(x) = HMAC_hash(x, key=salt, digest=md)" .ie n .IP "\fBH(x) = KMACxxx(x, key=salt, custom=""\s-1KDF"",\s0 outlen=mac_size)\fR" 4 .el .IP "\fBH(x) = KMACxxx(x, key=salt, custom=``\s-1KDF'',\s0 outlen=mac_size)\fR" 4 .IX Item "H(x) = KMACxxx(x, key=salt, custom=KDF, outlen=mac_size)" .PD .PP Both the \s-1HMAC\s0 and \s-1KMAC\s0 implementations set the key using the 'salt' value. The hash and \s-1HMAC\s0 also require the digest to be set. .SS "Identity" .IX Subsection "Identity" \&\*(L"\s-1SSKDF\*(R"\s0 is the name for this implementation; it can be used with the \fBEVP_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 This parameter is ignored for \s-1KMAC.\s0 .ie n .IP """mac"" (\fB\s-1OSSL_KDF_PARAM_MAC\s0\fR) <\s-1UTF8\s0 string>" 4 .el .IP "``mac'' (\fB\s-1OSSL_KDF_PARAM_MAC\s0\fR) <\s-1UTF8\s0 string>" 4 .IX Item "mac (OSSL_KDF_PARAM_MAC) " .PD 0 .ie n .IP """maclen"" (\fB\s-1OSSL_KDF_PARAM_MAC_SIZE\s0\fR) " 4 .el .IP "``maclen'' (\fB\s-1OSSL_KDF_PARAM_MAC_SIZE\s0\fR) " 4 .IX Item "maclen (OSSL_KDF_PARAM_MAC_SIZE) " .ie n .IP """salt"" (\fB\s-1OSSL_KDF_PARAM_SALT\s0\fR) " 4 .el .IP "``salt'' (\fB\s-1OSSL_KDF_PARAM_SALT\s0\fR) " 4 .IX Item "salt (OSSL_KDF_PARAM_SALT) " .PD These parameters work as described in \*(L"\s-1PARAMETERS\*(R"\s0 in \s-1\fBEVP_KDF\s0\fR\|(3). .ie n .IP """key"" (\fB\s-1EVP_KDF_CTRL_SET_KEY\s0\fR) " 4 .el .IP "``key'' (\fB\s-1EVP_KDF_CTRL_SET_KEY\s0\fR) " 4 .IX Item "key (EVP_KDF_CTRL_SET_KEY) " This parameter set the shared secret that is used for key derivation. .ie n .IP """info"" (\fB\s-1OSSL_KDF_PARAM_INFO\s0\fR) " 4 .el .IP "``info'' (\fB\s-1OSSL_KDF_PARAM_INFO\s0\fR) " 4 .IX Item "info (OSSL_KDF_PARAM_INFO) " This parameter sets an optional value for fixedinfo, also known as otherinfo. .SH "NOTES" .IX Header "NOTES" A context for \s-1SSKDF\s0 can be obtained by calling: .PP .Vb 2 \& EVP_KDF *kdf = EVP_KDF_fetch(NULL, "SSKDF", NULL); \& EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf); .Ve .PP The output length of an \s-1SSKDF\s0 is specified via the \fIkeylen\fR parameter to the \fBEVP_KDF_derive\fR\|(3) function. .SH "EXAMPLES" .IX Header "EXAMPLES" This example derives 10 bytes using H(x) = \s-1SHA\-256,\s0 with the secret key \*(L"secret\*(R" and fixedinfo value \*(L"label\*(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, "SSKDF", 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_KEY, \& "secret", (size_t)6); \& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO, \& "label", (size_t)5); \& *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 .PP This example derives 10 bytes using H(x) = \s-1HMAC\s0(\s-1SHA\-256\s0), with the secret key \*(L"secret\*(R", fixedinfo value \*(L"label\*(R" and salt \*(L"salt\*(R": .PP .Vb 4 \& EVP_KDF *kdf; \& EVP_KDF_CTX *kctx; \& unsigned char out[10]; \& OSSL_PARAM params[6], *p = params; \& \& kdf = EVP_KDF_fetch(NULL, "SSKDF", NULL); \& kctx = EVP_KDF_CTX_new(kdf); \& EVP_KDF_free(kdf); \& \& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC, \& SN_hmac, strlen(SN_hmac)); \& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST, \& SN_sha256, strlen(SN_sha256)); \& *p++ = OSSL_PARAM_construct_octet_string(EVP_KDF_CTRL_SET_KEY, \& "secret", (size_t)6); \& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO, \& "label", (size_t)5); \& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT, \& "salt", (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 .PP This example derives 10 bytes using H(x) = \s-1KMAC128\s0(x,salt,outlen), with the secret key \*(L"secret\*(R" fixedinfo value \*(L"label\*(R", salt of \*(L"salt\*(R" and \s-1KMAC\s0 outlen of 20: .PP .Vb 4 \& EVP_KDF *kdf; \& EVP_KDF_CTX *kctx; \& unsigned char out[10]; \& OSSL_PARAM params[6], *p = params; \& \& kdf = EVP_KDF_fetch(NULL, "SSKDF", NULL); \& kctx = EVP_KDF_CTX_new(kdf); \& EVP_KDF_free(kdf); \& \& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC, \& SN_kmac128, strlen(SN_kmac128)); \& *p++ = OSSL_PARAM_construct_octet_string(EVP_KDF_CTRL_SET_KEY, \& "secret", (size_t)6); \& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO, \& "label", (size_t)5); \& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT, \& "salt", (size_t)4); \& *p++ = OSSL_PARAM_construct_size_t(OSSL_KDF_PARAM_MAC_SIZE, (size_t)20); \& *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-1NIST\s0 SP800\-56Cr1. .SH "SEE ALSO" .IX Header "SEE ALSO" \&\s-1\fBEVP_KDF\s0\fR\|(3), \&\fBEVP_KDF_CTX_new\fR\|(3), \&\fBEVP_KDF_CTX_free\fR\|(3), \&\fBEVP_KDF_CTX_set_params\fR\|(3), \&\fBEVP_KDF_CTX_get_kdf_size\fR\|(3), \&\fBEVP_KDF_derive\fR\|(3), \&\*(L"\s-1PARAMETERS\*(R"\s0 in \s-1\fBEVP_KDF\s0\fR\|(3) .SH "HISTORY" .IX Header "HISTORY" This functionality was added in OpenSSL 3.0. .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2019\-2023 The OpenSSL Project Authors. All Rights Reserved. Copyright (c) 2019, Oracle and/or its affiliates. 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 .