DSA_SIG *DSA_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
int DSA_do_verify(const unsigned char *dgst, int dgst_len,
DSA_SIG *sig, DSA *dsa);
DESCRIPTION
DSA_do_sign() computes a digital signature on the len byte message
digest dgst using the private key dsa and returns it in a
newly allocated DSA_SIG structure.
DSA_sign_setup(3) may be used to precompute part
of the signing operation in case signature generation is
time-critical.
DSA_do_verify() verifies that the signature sig matches a given
message digest dgst of size len. dsa is the signer's public
key.
RETURN VALUES
DSA_do_sign() returns the signature, NULL on error. DSA_do_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).