NAME    [Toc]    [Back]

       DSA_sign, DSA_sign_setup, DSA_verify - DSA signatures

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]

       The  DSA_sign()  function  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 placed in *siglen.  The  sigret
       must point to DSA_size(dsa) bytes of memory.

       The  DSA_sign_setup()  function  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. The ctx is a preallocated
 BN_CTX or NULL.

       The DSA_verify() function verifies that the signature sigbuf
  of size siglen matches a given message digest dgst of
       size len. The dsa is the signer's public key.

       The type parameter is ignored.

       The  PRNG  must  be  seeded  before  the   DSA_sign()   or
       DSA_sign_setup() function is called.

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

RETURN VALUES    [Toc]    [Back]

       The  DSA_sign() and DSA_sign_setup() functions return 1 on
       success, 0 on error. The DSA_verify() function  returns  1
       for  a  valid signature, 0 for an incorrect signature, and
       -1  on  error.  The  error  codes  can  be  obtained  from
       ERR_get_error().

HISTORY    [Toc]    [Back]

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

SEE ALSO    [Toc]    [Back]

       Functions: dsa(3), err(3), rand(3), DSA_do_sign(3)



                                                      DSA_sign(3)