EVP_KDF-X942-ASN1(7ssl) OpenSSL EVP_KDF-X942-ASN1(7ssl)

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

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).

The output is considered to be keying material.

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

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".

The OpenSSL FIPS provider also supports the following parameters:

"fips-indicator" (OSSL_KDF_PARAM_FIPS_APPROVED_INDICATOR) <integer>
A getter that returns 1 if the operation is FIPS approved, or 0 otherwise. This may be used after calling EVP_KDF_derive. It returns 0 if "key-check" parameter is set to 0 and the check fails.
"key-check" (OSSL_KDF_PARAM_FIPS_KEY_CHECK) <integer>
The default value of 1 causes an error during EVP_KDF_CTX_set_params() if the length of used key-derivation key (OSSL_KDF_PARAM_KEY) is shorter than 112 bits. Setting this to zero will ignore the error and set the approved "fips-indicator" to 0. This option breaks FIPS compliance if it causes the approved "fips-indicator" to return 0.

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.

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);

ANS1 X9.42-2003 RFC 2631

EVP_KDF(3), EVP_KDF_CTX_new(3), EVP_KDF_CTX_free(3), EVP_KDF_CTX_set_params(3), EVP_KDF_CTX_get_kdf_size(3), EVP_KDF_derive(3), "PARAMETERS" in EVP_KDF(3)

This functionality was added in OpenSSL 3.0.

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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.

2024-10-23 3.4.0