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Title "EVP_KDF-SS 7" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
EVP_KDF-SS - The Single Step / One Step EVP_KDF implementation 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'. Subsection "Auxiliary function" The implementation uses a selectable auxiliary function H, which can be one of: Item "H(x) = hash(x, digest=md)"

0

Item "H(x) = HMAC_hash(x, key=salt, digest=md)" Item "H(x) = KMACxxx(x, key=salt, custom=KDF, outlen=mac_size)"

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.

Subsection "Identity" \*(L"\s-1SSKDF\*(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>"

This parameter is ignored for \s-1KMAC.\s0 Item "mac (OSSL_KDF_PARAM_MAC) <UTF8 string>"

0 Item "maclen (OSSL_KDF_PARAM_MAC_SIZE) <unsigned integer>" Item "salt (OSSL_KDF_PARAM_SALT) <octet string>"

These parameters work as described in \*(L"\s-1PARAMETERS\*(R"\s0 in \s-1EVP_KDF\s0\|(3). Item "key (EVP_KDF_CTRL_SET_KEY) <octet string>" This parameter set the shared secret that is used for key derivation. Item "info (OSSL_KDF_PARAM_INFO) <octet string>" This parameter sets an optional value for fixedinfo, also known as otherinfo.

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

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

The output length of an \s-1SSKDF\s0 is specified via the keylen parameter to the EVP_KDF_derive\|(3) function.

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":

.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

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":

.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

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:

.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

Header "CONFORMING TO" \s-1NIST\s0 SP800-56Cr1. 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_CTX_get_kdf_size\|(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 2019-2023 The OpenSSL Project Authors. All Rights Reserved. Copyright (c) 2019, Oracle and/or its affiliates. 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>.