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Title "EVP_KDF-X942-ASN1 7ossl" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
EVP_KDF-X942-ASN1 - The X9.42-2003 asn1 EVP_KDF implementation Header "DESCRIPTION" The \s-1EVP_KDF-X942-ASN1\s0 algorithm implements the key derivation function X942KDF-ASN1. It is used by \s-1DH\s0 KeyAgreement, to derive a key using input such as a shared secret key and other info. The other info is \s-1DER\s0 encoded data that contains a 32 bit counter as well as optional fields for \*(L"partyu-info\*(R", \*(L"partyv-info\*(R", \*(L"supp-pubinfo\*(R" and \*(L"supp-privinfo\*(R". This kdf is used by Cryptographic Message Syntax (\s-1CMS\s0). Subsection "Identity" \*(L"X942KDF-ASN1\*(R" or \*(L"X942KDF\*(R" 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). Item "secret (OSSL_KDF_PARAM_SECRET) <octet string>" The shared secret used for key derivation. This parameter sets the secret. Item "acvp-info (OSSL_KDF_PARAM_X942_ACVPINFO) <octet string>" This value should not be used in production and should only be used for \s-1ACVP\s0 testing. It is an optional octet string containing a combined \s-1DER\s0 encoded blob of any of the optional fields related to \*(L"partyu-info\*(R", \*(L"partyv-info\*(R", \*(L"supp-pubinfo\*(R" and \*(L"supp-privinfo\*(R". If it is specified then none of these other fields should be used. Item "partyu-info (OSSL_KDF_PARAM_X942_PARTYUINFO) <octet string>" An optional octet string containing public info contributed by the initiator. Item "ukm (OSSL_KDF_PARAM_UKM) <octet string>" An alias for \*(L"partyu-info\*(R". In \s-1CMS\s0 this is the user keying material. Item "partyv-info (OSSL_KDF_PARAM_X942_PARTYVINFO) <octet string>" An optional octet string containing public info contributed by the responder. Item "supp-pubinfo (OSSL_KDF_PARAM_X942_SUPP_PUBINFO) <octet string>" An optional octet string containing some additional, mutually-known public information. Setting this value also sets \*(L"use-keybits\*(R" to 0. Item "use-keybits (OSSL_KDF_PARAM_X942_USE_KEYBITS) <integer>" The default value of 1 will use the \s-1KEK\s0 key length (in bits) as the \*(L"supp-pubinfo\*(R". A value of 0 disables setting the \*(L"supp-pubinfo\*(R". Item "supp-privinfo (OSSL_KDF_PARAM_X942_SUPP_PRIVINFO) <octet string>" An optional octet string containing some additional, mutually-known private information. Item "cekalg (OSSL_KDF_PARAM_CEK_ALG) <UTF8 string>" This parameter sets the \s-1CEK\s0 wrapping algorithm name. Valid values are \*(L"\s-1AES-128-WRAP\*(R", \*(L"AES-192-WRAP\*(R", \*(L"AES-256-WRAP\*(R"\s0 and \*(L"\s-1DES3-WRAP\*(R".\s0

Header "NOTES" A context for X942KDF can be obtained by calling:

.Vb 2 EVP_KDF *kdf = EVP_KDF_fetch(NULL, "X942KDF", NULL); EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf); .Ve

The output length of an X942KDF is specified via the keylen parameter to the EVP_KDF_derive\|(3) function.

Header "EXAMPLES" This example derives 24 bytes, with the secret key \*(L"secret\*(R" and random user keying material:

.Vb 5 EVP_KDF_CTX *kctx; EVP_KDF_CTX *kctx; unsigned char out[192/8]; unsignred char ukm[64]; OSSL_PARAM params[5], *p = params; \& if (RAND_bytes(ukm, sizeof(ukm)) <= 0) error("RAND_bytes"); \& kdf = EVP_KDF_fetch(NULL, "X942KDF", NULL); if (kctx == NULL) error("EVP_KDF_fetch"); kctx = EVP_KDF_CTX_new(kdf); EVP_KDF_free(kdf); if (kctx == NULL) error("EVP_KDF_CTX_new"); \& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST, "SHA256", 0); *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SECRET, "secret", (size_t)6); *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_UKM, ukm, sizeof(ukm)); *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_CEK_ALG, "AES-256-WRAP, 0); *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-1ANS1 X9.42-2003 RFC 2631\s0 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 2019-2022 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>.