| =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 "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string> |
| |
| =item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string> |
| |
| These parameters work as described in L<EVP_KDF(3)/PARAMETERS>. |
| |
| =item "key" (B<OSSL_KDF_PARAM_KEY>) <octet string> |
| |
| The shared secret used for key derivation. This parameter sets the secret. |
| |
| =item "ukm" (B<OSSL_KDF_PARAM_UKM>) <octet string> |
| |
| This parameter is an optional random string that is provided |
| by the sender called "partyAInfo". |
| In CMS this is the user keying material. |
| |
| =item "cekalg" (B<OSSL_KDF_PARAM_CEK_ALG>) <UTF8 string> |
| |
| 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 I<keylen> |
| parameter to the L<EVP_KDF_derive(3)> 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<EVP_KDF(3)>, |
| L<EVP_KDF_CTX_new(3)>, |
| L<EVP_KDF_CTX_free(3)>, |
| L<EVP_KDF_CTX_set_params(3)>, |
| L<EVP_KDF_size(3)>, |
| L<EVP_KDF_derive(3)>, |
| L<EVP_KDF(3)/PARAMETERS> |
| |
| =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<https://www.openssl.org/source/license.html>. |
| |
| =cut |
