1=pod 2 3=head1 NAME 4 5EVP_PKEY-DSA, EVP_KEYMGMT-DSA - EVP_PKEY DSA keytype and algorithm support 6 7=head1 DESCRIPTION 8 9For B<DSA> the FIPS 186-4 standard specifies that the values used for FFC 10parameter generation are also required for parameter validation. 11This means that optional FFC domain parameter values for I<seed>, I<pcounter> 12and I<gindex> may need to be stored for validation purposes. For B<DSA> these 13fields are not stored in the ASN1 data so they need to be stored externally if 14validation is required. 15 16As part of FIPS 140-3 DSA is not longer FIPS approved for key generation and 17signature validation, but is still allowed for signature verification. 18 19=head2 DSA parameters 20 21The B<DSA> key type supports the FFC parameters (see 22L<EVP_PKEY-FFC(7)/FFC parameters>). 23 24It also supports the following parameters: 25 26=over 4 27 28=item "sign-check" (B<OSSL_PKEY_PARAM_FIPS_SIGN_CHECK>) <integer 29 30=item "fips-indicator" (B<OSSL_PKEY_PARAM_FIPS_APPROVED_INDICATOR>) <integer> 31 32See L<provider-keymgmt(7)/Common Information Parameters> for more information. 33 34=back 35 36=head2 DSA key generation parameters 37 38The B<DSA> key type supports the FFC key generation parameters (see 39L<EVP_PKEY-FFC(7)/FFC key generation parameters> 40 41The following restrictions apply to the "pbits" field: 42 43For "fips186_4" this must be either 2048 or 3072. 44For "fips186_2" this must be 1024. 45For "group" this can be any one of 2048, 3072, 4096, 6144 or 8192. 46 47=head2 DSA key validation 48 49For DSA keys, L<EVP_PKEY_param_check(3)> behaves in the following way: 50The OpenSSL FIPS provider conforms to the rules within the FIPS186-4 51standard for FFC parameter validation. For backwards compatibility the OpenSSL 52default provider uses a much simpler check (see below) for parameter validation, 53unless the seed parameter is set. 54 55For DSA keys, L<EVP_PKEY_param_check_quick(3)> behaves in the following way: 56A simple check of L and N and partial g is performed. The default provider 57also supports validation of legacy "fips186_2" keys. 58 59For DSA keys, L<EVP_PKEY_public_check(3)>, L<EVP_PKEY_private_check(3)> and 60L<EVP_PKEY_pairwise_check(3)> the OpenSSL default and FIPS providers conform to 61the rules within SP800-56Ar3 for public, private and pairwise tests respectively. 62 63=head1 EXAMPLES 64 65An B<EVP_PKEY> context can be obtained by calling: 66 67 EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_from_name(NULL, "DSA", NULL); 68 69The B<DSA> domain parameters can be generated by calling: 70 71 unsigned int pbits = 2048; 72 unsigned int qbits = 256; 73 int gindex = 1; 74 OSSL_PARAM params[5]; 75 EVP_PKEY *param_key = NULL; 76 EVP_PKEY_CTX *pctx = NULL; 77 78 pctx = EVP_PKEY_CTX_new_from_name(NULL, "DSA", NULL); 79 EVP_PKEY_paramgen_init(pctx); 80 81 params[0] = OSSL_PARAM_construct_uint("pbits", &pbits); 82 params[1] = OSSL_PARAM_construct_uint("qbits", &qbits); 83 params[2] = OSSL_PARAM_construct_int("gindex", &gindex); 84 params[3] = OSSL_PARAM_construct_utf8_string("digest", "SHA384", 0); 85 params[4] = OSSL_PARAM_construct_end(); 86 EVP_PKEY_CTX_set_params(pctx, params); 87 88 EVP_PKEY_generate(pctx, ¶m_key); 89 EVP_PKEY_CTX_free(pctx); 90 91 EVP_PKEY_print_params(bio_out, param_key, 0, NULL); 92 93A B<DSA> key can be generated using domain parameters by calling: 94 95 EVP_PKEY *key = NULL; 96 EVP_PKEY_CTX *gctx = NULL; 97 98 gctx = EVP_PKEY_CTX_new_from_pkey(NULL, param_key, NULL); 99 EVP_PKEY_keygen_init(gctx); 100 EVP_PKEY_generate(gctx, &key); 101 EVP_PKEY_CTX_free(gctx); 102 EVP_PKEY_print_private(bio_out, key, 0, NULL); 103 104 105=head1 CONFORMING TO 106 107The following sections of FIPS186-4: 108 109=over 4 110 111=item A.1.1.2 Generation of Probable Primes p and q Using an Approved Hash Function. 112 113=item A.2.3 Generation of canonical generator g. 114 115=item A.2.1 Unverifiable Generation of the Generator g. 116 117=back 118 119=head1 SEE ALSO 120 121L<EVP_PKEY-FFC(7)>, 122L<EVP_SIGNATURE-DSA(7)> 123L<EVP_PKEY(3)>, 124L<provider-keymgmt(7)>, 125L<EVP_KEYMGMT(3)>, 126L<OSSL_PROVIDER-default(7)>, 127L<OSSL_PROVIDER-FIPS(7)> 128 129=head1 HISTORY 130 131DSA Key generation and signature generation are no longer FIPS approved in 132OpenSSL 3.4. See L<fips_module(7)/FIPS indicators> for more information. 133 134=head1 COPYRIGHT 135 136Copyright 2020-2024 The OpenSSL Project Authors. All Rights Reserved. 137 138Licensed under the Apache License 2.0 (the "License"). You may not use 139this file except in compliance with the License. You can obtain a copy 140in the file LICENSE in the source distribution or at 141L<https://www.openssl.org/source/license.html>. 142 143=cut 144
