Updated: 2022/Sep/29
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EVP_PKEY-DSA(7) OpenSSL EVP_PKEY-DSA(7)
NAME
EVP_PKEY-DSA, EVP_KEYMGMT-DSA - EVP_PKEY DSA keytype and algorithm
support
DESCRIPTION
For DSA the FIPS186-4 standard specifies that the values used for FFC
parameter generation are also required for parameter validation. This
means that optional FFC domain parameter values for seed, pcounter and
gindex may need to be stored for validation purposes. For DSA these
fields are not stored in the ASN1 data so they need to be stored
externally if validation is required.
DSA parameters
The DSA key type supports the FFC parameters (see "FFC parameters" in
EVP_PKEY-FFC(7)).
DSA key generation parameters
The DSA key type supports the FFC key generation parameters (see "FFC
key generation parameters" in EVP_PKEY-FFC(7)
The following restrictions apply to the "pbits" field:
For "fips186_4" this must be either 2048 or 3072. For "fips186_2" this
must be 1024. For "group" this can be any one of 2048, 3072, 4096,
6144 or 8192.
DSA key validation
For DSA keys, EVP_PKEY_param_check(3) behaves in the following way: The
OpenSSL FIPS provider conforms to the rules within the FIPS186-4
standard for FFC parameter validation. For backwards compatibility the
OpenSSL default provider uses a much simpler check (see below) for
parameter validation, unless the seed parameter is set.
For DSA keys, EVP_PKEY_param_check_quick(3) behaves in the following
way: A simple check of L and N and partial g is performed. The default
provider also supports validation of legacy "fips186_2" keys.
For DSA keys, EVP_PKEY_public_check(3), EVP_PKEY_private_check(3) and
EVP_PKEY_pairwise_check(3) the OpenSSL default and FIPS providers
conform to the rules within SP800-56Ar3 for public, private and
pairwise tests respectively.
EXAMPLES
An EVP_PKEY context can be obtained by calling:
EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_from_name(NULL, "DSA", NULL);
The DSA domain parameters can be generated by calling:
unsigned int pbits = 2048;
unsigned int qbits = 256;
int gindex = 1;
OSSL_PARAM params[5];
EVP_PKEY *param_key = NULL;
EVP_PKEY_CTX *pctx = NULL;
pctx = EVP_PKEY_CTX_new_from_name(NULL, "DSA", NULL);
EVP_PKEY_paramgen_init(pctx);
params[0] = OSSL_PARAM_construct_uint("pbits", &pbits);
params[1] = OSSL_PARAM_construct_uint("qbits", &qbits);
params[2] = OSSL_PARAM_construct_int("gindex", &gindex);
params[3] = OSSL_PARAM_construct_utf8_string("digest", "SHA384", 0);
params[4] = OSSL_PARAM_construct_end();
EVP_PKEY_CTX_set_params(pctx, params);
EVP_PKEY_generate(pctx, ¶m_key);
EVP_PKEY_CTX_free(pctx);
EVP_PKEY_print_params(bio_out, param_key, 0, NULL);
A DSA key can be generated using domain parameters by calling:
EVP_PKEY *key = NULL;
EVP_PKEY_CTX *gctx = NULL;
gctx = EVP_PKEY_CTX_new_from_pkey(NULL, param_key, NULL);
EVP_PKEY_keygen_init(gctx);
EVP_PKEY_generate(gctx, &key);
EVP_PKEY_CTX_free(gctx);
EVP_PKEY_print_private(bio_out, key, 0, NULL);
CONFORMING TO
The following sections of FIPS186-4:
A.1.1.2 Generation of Probable Primes p and q Using an Approved Hash
Function.
A.2.3 Generation of canonical generator g.
A.2.1 Unverifiable Generation of the Generator g.
SEE ALSO
EVP_PKEY-FFC(7), EVP_SIGNATURE-DSA(7) EVP_PKEY(3), provider-keymgmt(7),
EVP_KEYMGMT(3), OSSL_PROVIDER-default(7), OSSL_PROVIDER-FIPS(7)
COPYRIGHT
Copyright 2020-2022 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
<https://www.openssl.org/source/license.html>.
3.0.12 2023-05-07 EVP_PKEY-DSA(7)