NAME

EVP_KDF-X942-ASN1 - The X9.42-2003 asn1 EVP_KDF implementation

DESCRIPTION

The EVP_KDF-X942-ASN1 algorithm implements the key derivation function X942KDF-ASN1. It is used by 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 as well as optional fields for partyu-info, partyv-info, supp-pubinfo and supp-privinfo. This kdf is used by Cryptographic Message Syntax (CMS).

Identity

X942KDF-ASN1 or X942KDF is the name for this implementation; it can be used with the EVP_KDF_fetch() function.

Supported parameters

The supported parameters are:

"properties" (OSSL_KDF_PARAM_PROPERTIES) <UTF8 string>

"digest" (OSSL_KDF_PARAM_DIGEST) <UTF8 string>

These parameters work as described in PARAMETERS in EVP_KDF (3).

"secret" (OSSL_KDF_PARAM_SECRET) <octet string>: The shared secret used for key derivation. This parameter sets the secret.
"acvp-info" (OSSL_KDF_PARAM_X942_ACVPINFO) <octet string>: This value should not be used in production and should only be used for ACVP testing. It is an optional octet string containing a combined DER encoded blob of any of the optional fields related to partyu-info, partyv-info, supp-pubinfo and supp-privinfo. If it is specified then none of these other fields should be used.
"partyu-info" (OSSL_KDF_PARAM_X942_PARTYUINFO) <octet string>: An optional octet string containing public info contributed by the initiator.
"ukm" (OSSL_KDF_PARAM_UKM) <octet string>: An alias for partyu-info. In CMS this is the user keying material.
"partyv-info" (OSSL_KDF_PARAM_X942_PARTYVINFO) <octet string>: An optional octet string containing public info contributed by the responder.
"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 use-keybits to 0.
"use-keybits" (OSSL_KDF_PARAM_X942_USE_KEYBITS) <integer>: The default value of 1 will use the KEK key length (in bits) as the supp-pubinfo. A value of 0 disables setting the supp-pubinfo.
"supp-privinfo" (OSSL_KDF_PARAM_X942_SUPP_PRIVINFO) <octet string>: An optional octet string containing some additional, mutually-known private information.
"cekalg" (OSSL_KDF_PARAM_CEK_ALG) <UTF8 string>: This parameter sets the CEK wrapping algorithm name. Valid values are AES-128-WRAP, AES-192-WRAP, AES-256-WRAP and DES3-WRAP.

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 keylen parameter to the EVP_KDF_derive (3) function.

EXAMPLES

This example derives 24 bytes, with the secret key secret and 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); 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);

CONFORMING TO

ANS1 X9.42-2003 RFC 2631

HISTORY

This functionality was added in OpenSSL 3.0.

COPYRIGHT

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 <https://www.openssl.org/source/license.html>.