| =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 |
