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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

  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 pre-allocated 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

  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

  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

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

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