EVP_PKEY-DSA, EVP_KEYMGMT-DSA - EVP_PKEY DSA keytype and algorithm support
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.
The DSA key type supports the FFC parameters (see FFC parameters in EVP_PKEY-FFC (7)).
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.
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.
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);
The following sections of FIPS186-4:
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)
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