/usr/man2/cat.3/DSA_sign_setup.3.Z(/usr/man2/cat.3/DSA_sign_setup.3.Z)

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 opera-
       tion in case signature generation is time-critical. It expects dsa to
       contain DSA parameters. It places the precomputed values in newly allo-
       cated 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.  The pre-
       computed values from DSA_sign_setup() MUST NOT be used for more than
       one signature: using the same dsa->kinv and dsa->r pair twice under the
       same private key on different plaintexts will result in permanently
       exposing the DSA private key.

       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 signa-
       ture 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.

1.0.2t                            2019-09-10                       DSA_sign(3)
See also DSA_sign(3)
See also DSA_verify(3)