openssl/doc/crypto/DSA_sign.pod
Richard Levitte 6859cf7459 It makes more sense to refer to specific function manuals than the concept
manual when the specific function is refered to in the current manual text.
This correction was originally introduced in OpenBSD's tracking of OpenSSL.
2002-09-25 13:33:28 +00:00

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=pod
=head1 NAME
DSA_sign, DSA_sign_setup, DSA_verify - DSA signatures
=head1 SYNOPSIS
#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);
=head1 DESCRIPTION
DSA_sign() computes a digital signature on the B<len> byte message
digest B<dgst> using the private key B<dsa> and places its ASN.1 DER
encoding at B<sigret>. The length of the signature is places in
*B<siglen>. B<sigret> must point to DSA_size(B<dsa>) bytes of memory.
DSA_sign_setup() may be used to precompute part of the signing
operation in case signature generation is time-critical. It expects
B<dsa> to contain DSA parameters. It places the precomputed values
in newly allocated B<BIGNUM>s at *B<kinvp> and *B<rp>, after freeing
the old ones unless *B<kinvp> and *B<rp> are NULL. These values may
be passed to DSA_sign() in B<dsa-E<gt>kinv> and B<dsa-E<gt>r>.
B<ctx> is a pre-allocated B<BN_CTX> or NULL.
DSA_verify() verifies that the signature B<sigbuf> of size B<siglen>
matches a given message digest B<dgst> of size B<len>.
B<dsa> is the signer's public key.
The B<type> parameter is ignored.
The PRNG must be seeded before DSA_sign() (or DSA_sign_setup())
is called.
=head1 RETURN VALUES
DSA_sign() and DSA_sign_setup() return 1 on success, 0 on error.
DSA_verify() returns 1 for a valid signature, 0 for an incorrect
signature and -1 on error. The error codes can be obtained by
L<ERR_get_error(3)|ERR_get_error(3)>.
=head1 CONFORMING TO
US Federal Information Processing Standard FIPS 186 (Digital Signature
Standard, DSS), ANSI X9.30
=head1 SEE ALSO
L<dsa(3)|dsa(3)>, L<ERR_get_error(3)|ERR_get_error(3)>, L<rand(3)|rand(3)>,
L<DSA_do_sign(3)|DSA_do_sign(3)>
=head1 HISTORY
DSA_sign() and DSA_verify() are available in all versions of SSLeay.
DSA_sign_setup() was added in SSLeay 0.8.
=cut