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.\" ========================================================================
.\"
.IX Title "DSA_SIGN 3"
.TH DSA_SIGN 3 "2023-09-11" "1.1.1w" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
DSA_sign, DSA_sign_setup, DSA_verify \- DSA signatures
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/dsa.h>
\&
\& int DSA_sign(int type, const unsigned char *dgst, int len,
\&              unsigned char *sigret, unsigned int *siglen, DSA *dsa);
\&
\& int DSA_sign_setup(DSA *dsa, BN_CTX *ctx, BIGNUM **kinvp, BIGNUM **rp);
\&
\& int DSA_verify(int type, const unsigned char *dgst, int len,
\&                unsigned char *sigbuf, int siglen, DSA *dsa);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBDSA_sign()\fR computes a digital signature on the \fBlen\fR byte message
digest \fBdgst\fR using the private key \fBdsa\fR and places its \s-1ASN.1 DER\s0
encoding at \fBsigret\fR. The length of the signature is places in
*\fBsiglen\fR. \fBsigret\fR must point to DSA_size(\fBdsa\fR) bytes of memory.
.PP
\&\fBDSA_sign_setup()\fR is defined only for backward binary compatibility and
should not be used.
Since OpenSSL 1.1.0 the \s-1DSA\s0 type is opaque and the output of
\&\fBDSA_sign_setup()\fR cannot be used anyway: calling this function will only
cause overhead, and does not affect the actual signature
(pre\-)computation.
.PP
\&\fBDSA_verify()\fR verifies that the signature \fBsigbuf\fR of size \fBsiglen\fR
matches a given message digest \fBdgst\fR of size \fBlen\fR.
\&\fBdsa\fR is the signer's public key.
.PP
The \fBtype\fR parameter is ignored.
.PP
The random generator must be seeded when \fBDSA_sign()\fR (or \fBDSA_sign_setup()\fR)
is called.
If the automatic seeding or reseeding of the OpenSSL \s-1CSPRNG\s0 fails due to
external circumstances (see \s-1\fBRAND\s0\fR\|(7)), the operation will fail.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBDSA_sign()\fR and \fBDSA_sign_setup()\fR return 1 on success, 0 on error.
\&\fBDSA_verify()\fR returns 1 for a valid signature, 0 for an incorrect
signature and \-1 on error. The error codes can be obtained by
\&\fBERR_get_error\fR\|(3).
.SH "CONFORMING TO"
.IX Header "CONFORMING TO"
\&\s-1US\s0 Federal Information Processing Standard \s-1FIPS 186\s0 (Digital Signature
Standard, \s-1DSS\s0), \s-1ANSI X9.30\s0
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBDSA_new\fR\|(3), \fBERR_get_error\fR\|(3), \fBRAND_bytes\fR\|(3),
\&\fBDSA_do_sign\fR\|(3),
\&\s-1\fBRAND\s0\fR\|(7)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2000\-2019 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (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>.