NAME    [Toc]    [Back]

       DSA_sign, DSA_sign_setup, DSA_verify - DSA signatures

LIBRARY    [Toc]    [Back]

       libcrypto, -lcrypto

SYNOPSIS    [Toc]    [Back]

        #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    [Toc]    [Back]

       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 timecritical.
 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    [Toc]    [Back]

       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    [Toc]    [Back]

       US Federal Information Processing Standard FIPS 186 (Digital
 Signature Standard, DSS), ANSI X9.30

SEE ALSO    [Toc]    [Back]

       openssl_dsa(3), openssl_err(3), openssl_rand(3),
       DSA_do_sign(3)

HISTORY    [Toc]    [Back]

       DSA_sign() and DSA_verify() are available in all versions
       of SSLeay.  DSA_sign_setup() was added in SSLeay 0.8.



2000-07-22                    0.9.6g                  DSA_sign(3)