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DSA_sign(3)                         OpenSSL                        DSA_sign(3)



NAME
       DSA_sign, DSA_sign_setup, DSA_verify - DSA signatures

LIBRARY
       libcrypto, -lcrypto

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
       openssl_dsa(3), ERR_get_error(3), openssl_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.



1.0.1u                            2009-07-19                       DSA_sign(3)