/usr/man/cat.3/DSA_verify.3

DSA_sign(3)                  OpenSSL                  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.  The precomputed 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 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

1.0.2t               Last change: 2019-09-10                    1

DSA_sign(3)                  OpenSSL                  DSA_sign(3)

     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               Last change: 2019-09-10                    2

See also DSA_sign(3)
See also DSA_sign_setup(3)