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.\" $OpenBSD: DSA_sign.3,v 1.8 2018/03/27 17:35:50 schwarze Exp $
.\" OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
.\"
.\" This file was written by Ulf Moeller <ulf@openssl.org>.
.\" Copyright (c) 2000 The OpenSSL Project. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\"
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\"
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in
.\" the documentation and/or other materials provided with the
.\" distribution.
.\"
.\" 3. All advertising materials mentioning features or use of this
.\" software must display the following acknowledgment:
.\" "This product includes software developed by the OpenSSL Project
.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
.\"
.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
.\" endorse or promote products derived from this software without
.\" prior written permission. For written permission, please contact
.\" openssl-core@openssl.org.
.\"
.\" 5. Products derived from this software may not be called "OpenSSL"
.\" nor may "OpenSSL" appear in their names without prior written
.\" permission of the OpenSSL Project.
.\"
.\" 6. Redistributions of any form whatsoever must retain the following
.\" acknowledgment:
.\" "This product includes software developed by the OpenSSL Project
.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)"
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
.\" OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd $Mdocdate: March 27 2018 $
.Dt DSA_SIGN 3
.Os
.Sh NAME
.Nm DSA_sign ,
.Nm DSA_sign_setup ,
.Nm DSA_verify
.Nd DSA signatures
.Sh SYNOPSIS
.In openssl/dsa.h
.Ft int
.Fo DSA_sign
.Fa "int type"
.Fa "const unsigned char *dgst"
.Fa "int len"
.Fa "unsigned char *sigret"
.Fa "unsigned int *siglen"
.Fa "DSA *dsa"
.Fc
.Ft int
.Fo DSA_sign_setup
.Fa "DSA *dsa"
.Fa "BN_CTX *ctx"
.Fa "BIGNUM **kinvp"
.Fa "BIGNUM **rp"
.Fc
.Ft int
.Fo DSA_verify
.Fa "int type"
.Fa "const unsigned char *dgst"
.Fa "int len"
.Fa "unsigned char *sigbuf"
.Fa "int siglen"
.Fa "DSA *dsa"
.Fc
.Sh DESCRIPTION
.Fn DSA_sign
computes a digital signature on the
.Fa len
byte message digest
.Fa dgst
using the private key
.Fa dsa
and places its ASN.1 DER encoding at
.Fa sigret .
The length of the signature is placed in
.Pf * Fa siglen .
.Fa sigret
must point to
.Fn DSA_size dsa
bytes of memory.
.Pp
.Fn DSA_sign_setup
may be used to precompute part of the signing operation in case
signature generation is time-critical.
It expects
.Fa dsa
to contain DSA parameters.
It places the precomputed values in newly allocated
.Vt BIGNUM Ns s
at
.Pf * Fa kinvp
and
.Pf * Fa rp ,
after freeing the old ones unless
.Fa kinvp
and
.Fa rp
are
.Dv NULL .
These values may be passed to
.Fn DSA_sign
in
.Fa dsa->kinv
and
.Sy dsa->r .
.Fa ctx
is a pre-allocated
.Vt BN_CTX
or
.Dv NULL .
.Pp
.Fn DSA_verify
verifies that the signature
.Fa sigbuf
of size
.Fa siglen
matches a given message digest
.Fa dgst
of size
.Fa len .
.Fa dsa
is the signer's public key.
.Pp
The
.Fa type
parameter is ignored.
.Sh RETURN VALUES
.Fn DSA_sign
and
.Fn DSA_sign_setup
return 1 on success or 0 on error.
.Fn DSA_verify
returns 1 for a valid signature, 0 for an incorrect signature,
and -1 on error.
The error codes can be obtained by
.Xr ERR_get_error 3 .
.Sh SEE ALSO
.Xr DSA_do_sign 3 ,
.Xr DSA_get0_key 3 ,
.Xr DSA_new 3 ,
.Xr ERR_get_error 3 ,
.Xr RAND_bytes 3
.Sh STANDARDS
US Federal Information Processing Standard FIPS 186 (Digital Signature
Standard, DSS), ANSI X9.30
.Sh HISTORY
.Fn DSA_sign
and
.Fn DSA_verify
first appeared in SSLeay 0.6.0.
.Fn DSA_sign_setup
first appeared in SSLeay 0.8.0.
All these functions have been available since
.Ox 2.4 .
|
