=pod =head1 NAME EVP_KDF-X942 - The X9.42-2001 asn1 EVP_KDF implementation =head1 DESCRIPTION The EVP_KDF-X942 algorithm implements the key derivation function (X942KDF). X942KDF is used by Cryptographic Message Syntax (CMS) for DH KeyAgreement, to derive a key using input such as a shared secret key and other info. The other info is DER encoded data that contains a 32 bit counter. =head2 Identity "X942KDF" is the name for this implementation; it can be used with the EVP_KDF_fetch() function. =head2 Supported parameters The supported parameters are: =over 4 =item B ("properties") =item B ("digest") These parameters work as described in L. =item B ("key") The shared secret used for key derivation. This parameter sets the secret. =item B ("ukm") This parameter is an optional random string that is provided by the sender called "partyAInfo". In CMS this is the user keying material. =item B ("cekalg") This parameter sets the CEK wrapping algorithm name. =back =head1 NOTES A context for X942KDF can be obtained by calling: EVP_KDF *kdf = EVP_KDF_fetch(NULL, "X942KDF", NULL); EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf); The output length of an X942KDF is specified via the C parameter to the L function. =head1 EXAMPLES This example derives 24 bytes, with the secret key "secret" and a random user keying material: 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); if (kctx == NULL) error("EVP_KDF_CTX_new"); 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_UKM, ukm, sizeof(ukm)); *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_CEK_ALG, SN_id_smime_alg_CMS3DESwrap, strlen(SN_id_smime_alg_CMS3DESwrap)); *p = OSSL_PARAM_construct_end(); if (EVP_KDF_CTX_set_params(kctx, params) <= 0) error("EVP_KDF_CTX_set_params"); if (EVP_KDF_derive(kctx, out, sizeof(out)) <= 0) error("EVP_KDF_derive"); EVP_KDF_CTX_free(kctx); =head1 CONFORMING TO RFC 2631 =head1 SEE ALSO L, L, L, L, L, L, L =head1 HISTORY This functionality was added to OpenSSL 3.0. =head1 COPYRIGHT Copyright 2019 The OpenSSL Project Authors. All Rights Reserved. Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at L. =cut