DSA_sign(3)

     DSA_sign(3)            0.9.6h (2002-09-25)            DSA_sign(3)

     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)

     Page 1                                         (printed 1/19/103)

     DSA_sign(3)            0.9.6h (2002-09-25)            DSA_sign(3)

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

     Page 2                                         (printed 1/19/103)