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Title "EVP_PKEY-DSA 7" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
EVP_PKEY-DSA, EVP_KEYMGMT-DSA - EVP_PKEY DSA keytype and algorithm support Header "DESCRIPTION" For \s-1DSA\s0 the \s-1FIPS186-4\s0 standard specifies that the values used for \s-1FFC\s0 parameter generation are also required for parameter validation. This means that optional \s-1FFC\s0 domain parameter values for seed, pcounter and gindex may need to be stored for validation purposes. For \s-1DSA\s0 these fields are not stored in the \s-1ASN1\s0 data so they need to be stored externally if validation is required. Subsection "DSA parameters" The \s-1DSA\s0 key type supports the \s-1FFC\s0 parameters (see \*(L"\s-1FFC\s0 parameters\*(R" in \s-1EVP_PKEY-FFC\s0\|(7)). Subsection "DSA key generation parameters" The \s-1DSA\s0 key type supports the \s-1FFC\s0 key generation parameters (see \*(L"\s-1FFC\s0 key generation parameters\*(R" in \s-1EVP_PKEY-FFC\s0\|(7)

The following restrictions apply to the \*(L"pbits\*(R" field:

For \*(L"fips186_4\*(R" this must be either 2048 or 3072. For \*(L"fips186_2\*(R" this must be 1024. For \*(L"group\*(R" this can be any one of 2048, 3072, 4096, 6144 or 8192.

Subsection "DSA key validation" For \s-1DSA\s0 keys, EVP_PKEY_param_check\|(3) behaves in the following way: The OpenSSL \s-1FIPS\s0 provider conforms to the rules within the \s-1FIPS186-4\s0 standard for \s-1FFC\s0 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 \s-1DSA\s0 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 \*(L"fips186_2\*(R" keys.

For \s-1DSA\s0 keys, EVP_PKEY_public_check\|(3), EVP_PKEY_private_check\|(3) and \fBEVP_PKEY_pairwise_check\|(3) the OpenSSL default and \s-1FIPS\s0 providers conform to the rules within SP800-56Ar3 for public, private and pairwise tests respectively.

Header "EXAMPLES" An \s-1EVP_PKEY\s0 context can be obtained by calling:

.Vb 1 EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_from_name(NULL, "DSA", NULL); .Ve

The \s-1DSA\s0 domain parameters can be generated by calling:

.Vb 6 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, &param_key); EVP_PKEY_CTX_free(pctx); \& EVP_PKEY_print_params(bio_out, param_key, 0, NULL); .Ve

A \s-1DSA\s0 key can be generated using domain parameters by calling:

.Vb 2 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); .Ve

Header "CONFORMING TO" The following sections of \s-1FIPS186-4:\s0 Item "A.1.1.2 Generation of Probable Primes p and q Using an Approved Hash Function."

0

Item "A.2.3 Generation of canonical generator g." Item "A.2.1 Unverifiable Generation of the Generator g."

Header "SEE ALSO" \s-1EVP_PKEY-FFC\s0\|(7), \s-1EVP_SIGNATURE-DSA\s0\|(7) \s-1EVP_PKEY\s0\|(3), \fBprovider-keymgmt\|(7), \s-1EVP_KEYMGMT\s0\|(3), \fBOSSL_PROVIDER-default\|(7), \s-1OSSL_PROVIDER-FIPS\s0\|(7) Header "COPYRIGHT" Copyright 2020-2022 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.