NAME
DSA_sign, DSA_sign_setup, DSA_verify — DSA signatures
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);
DESCRIPTION
DSA_sign() computes a digital signature on the len byte
message digest dgst using the private key dsa and places
its ASN.1 DER encoding at sigret. The length
of the signature is places in *siglen. sigret must
point to DSA_size(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 dsa to
contain DSA parameters. It places the precomputed values in newly
allocated BIGNUMs at *kinvp and
*rp, after freeing the old ones unless *kinvp and
*rp are NULL. These values may be passed to
DSA_sign() in dsa->kinv and dsa->r. ctx is
a pre-allocated BN_CTX or NULL.
DSA_verify() verifies that the signature sigbuf of
size siglen matches a given message digest dgst of
size len. dsa is the signer's
public key.
The type parameter is ignored.
The PRNG must be seeded before DSA_sign() (or DSA_sign_setup())
is called.
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 ERR_get_error(3).
CONFORMING TO
US Federal Information Processing Standard FIPS 186 (Digital
Signature Standard, DSS), ANSI X9.30
SEE ALSO
dsa(3), ERR_get_error(3), rand(3), DSA_do_sign(3)
HISTORY
DSA_sign() and DSA_verify() are available in all versions
of SSLeay. DSA_sign_setup() was added in SSLeay 0.8.
