Android_verify/third_party/android-libs/share/man/man7/EVP_PKEY-DSA.7ossl

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.\" ========================================================================
.\"
.IX Title "EVP_PKEY-DSA 7ossl"
.TH EVP_PKEY-DSA 7ossl "2024-09-03" "3.3.2" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH "NAME"
EVP_PKEY\-DSA, EVP_KEYMGMT\-DSA \- EVP_PKEY DSA keytype and algorithm support
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
For \fB\s-1DSA\s0\fR 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 \fIseed\fR, \fIpcounter\fR
and \fIgindex\fR may need to be stored for validation purposes. For \fB\s-1DSA\s0\fR these
fields are not stored in the \s-1ASN1\s0 data so they need to be stored externally if
validation is required.
.SS "\s-1DSA\s0 parameters"
.IX Subsection "DSA parameters"
The \fB\s-1DSA\s0\fR key type supports the \s-1FFC\s0 parameters (see
\&\*(L"\s-1FFC\s0 parameters\*(R" in \s-1\fBEVP_PKEY\-FFC\s0\fR\|(7)).
.SS "\s-1DSA\s0 key generation parameters"
.IX Subsection "DSA key generation parameters"
The \fB\s-1DSA\s0\fR key type supports the \s-1FFC\s0 key generation parameters (see
\&\*(L"\s-1FFC\s0 key generation parameters\*(R" in \s-1\fBEVP_PKEY\-FFC\s0\fR\|(7)
.PP
The following restrictions apply to the \*(L"pbits\*(R" field:
.PP
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.
.SS "\s-1DSA\s0 key validation"
.IX Subsection "DSA key validation"
For \s-1DSA\s0 keys, \fBEVP_PKEY_param_check\fR\|(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.
.PP
For \s-1DSA\s0 keys, \fBEVP_PKEY_param_check_quick\fR\|(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.
.PP
For \s-1DSA\s0 keys, \fBEVP_PKEY_public_check\fR\|(3), \fBEVP_PKEY_private_check\fR\|(3) and
\&\fBEVP_PKEY_pairwise_check\fR\|(3) the OpenSSL default and \s-1FIPS\s0 providers conform to
the rules within SP800\-56Ar3 for public, private and pairwise tests respectively.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
An \fB\s-1EVP_PKEY\s0\fR context can be obtained by calling:
.PP
.Vb 1
\&    EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_from_name(NULL, "DSA", NULL);
.Ve
.PP
The \fB\s-1DSA\s0\fR domain parameters can be generated by calling:
.PP
.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
.PP
A \fB\s-1DSA\s0\fR key can be generated using domain parameters by calling:
.PP
.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
.SH "CONFORMING TO"
.IX Header "CONFORMING TO"
The following sections of \s-1FIPS186\-4:\s0
.IP "A.1.1.2 Generation of Probable Primes p and q Using an Approved Hash Function." 4
.IX Item "A.1.1.2 Generation of Probable Primes p and q Using an Approved Hash Function."
.PD 0
.IP "A.2.3 Generation of canonical generator g." 4
.IX Item "A.2.3 Generation of canonical generator g."
.IP "A.2.1 Unverifiable Generation of the Generator g." 4
.IX Item "A.2.1 Unverifiable Generation of the Generator g."
.PD
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\s-1\fBEVP_PKEY\-FFC\s0\fR\|(7),
\&\s-1\fBEVP_SIGNATURE\-DSA\s0\fR\|(7)
\&\s-1\fBEVP_PKEY\s0\fR\|(3),
\&\fBprovider\-keymgmt\fR\|(7),
\&\s-1\fBEVP_KEYMGMT\s0\fR\|(3),
\&\fBOSSL_PROVIDER\-default\fR\|(7),
\&\s-1\fBOSSL_PROVIDER\-FIPS\s0\fR\|(7)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2020\-2021 The OpenSSL Project Authors. All Rights Reserved.
.PP
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>.