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DSA_set_default_openssl_method(3)
NAME
  DSA_set_method, DSA_set_default_openssl_method,
  DSA_get_default_openssl_method, DSA_new_method, DSA_OpenSSL - Select DSA
  method

SYNOPSIS
  #include <openssl/dsa.h>
  #include <openssl/engine.h>

  void DSA_set_default_openssl_method(
	  DSA_METHOD *meth );

  DSA_METHOD *DSA_get_default_openssl_method(
	  void );

  int DSA_set_method(
	  DSA *dsa, ENGINE *engine );

  DSA *DSA_new_method(
	  ENGINE *engine );

  DSA_METHOD *DSA_OpenSSL(
	  void );

DESCRIPTION
  A DSA_METHOD specifies the functions that OpenSSL uses for DSA operations.
  By modifying the method, alternative implementations such as hardware
  accelerators can be used.

  Initially, the default is the OpenSSL internal implementation. The
  DSA_OpenSSL() function returns a pointer to that method.

  The DSA_set_default_openssl_method() function makes meth the default method
  for all DSA structures created later.	 This is true only while the default
  engine for DSA operations remains as openssl.	 ENGINEs provide an
  encapsulation for implementations of one or more algorithms at a time, and
  all the DSA functions mentioned here operate within the scope of the
  default openssl engine.

  The DSA_get_default_openssl_method() function returns a pointer to the
  current default method for the openssl engine.

  The DSA_set_method() selects engine for all operations using the structure
  dsa.

  The DSA_new_method() function allocates and initializes a DSA structure so
  that engine will be used for the DSA operations. If engine is NULL, the
  default engine for DSA operations is used.

THE DSA_METHOD STRUCTURE
  struct  {	 /* name of the implementation */	  const char *name;

	    /* sign */
	       DSA_SIG *(*dsa_do_sign)(const unsigned char *dgst, int dlen,
					DSA *dsa);

	    /* pre-compute k^-1 and r */
	       int (*dsa_sign_setup)(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
					BIGNUM **rp);

	    /* verify */
	       int (*dsa_do_verify)(const unsigned char *dgst, int dgst_len,
					DSA_SIG *sig, DSA *dsa);

	    /* compute rr = a1^p1 * a2^p2 mod m (May be NULL for some
						 implementations) */
	       int (*dsa_mod_exp)(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1,
					BIGNUM *a2, BIGNUM *p2, BIGNUM *m,
					BN_CTX *ctx, BN_MONT_CTX *in_mont);

	    /* compute r = a ^ p mod m (May be NULL for some implementations) */
	       int (*bn_mod_exp)(DSA *dsa, BIGNUM *r, BIGNUM *a,
					const BIGNUM *p, const BIGNUM *m,
					BN_CTX *ctx, BN_MONT_CTX *m_ctx);

	    /* called at DSA_new */
	       int (*init)(DSA *DSA);

	    /* called at DSA_free */
	       int (*finish)(DSA *DSA);

	       int flags;

	       char *app_data; /* ?? */

	} DSA_METHOD;

RETURN VALUES
  The DSA_OpenSSL() and DSA_get_default_openssl_method() functions return
  pointers to the respective DSA_METHODs.

  The DSA_set_default_openssl_method() function returns no value.

  The DSA_set_method() function returns non-zero if the ENGINE associated
  with dsa was successfully changed to engine.

  The DSA_new_method() function returns NULL and sets an error code that can
  be obtained from ERR_get_error() if the allocation fails. Otherwise it
  returns a pointer to the newly allocated structure.

HISTORY
  The DSA_set_default_method(), DSA_get_default_method(), DSA_set_method(),
  DSA_new_method(), and DSA_OpenSSL() functions were added in OpenSSL 0.9.4.

  The DSA_set_default_openssl_method() and DSA_get_default_openssl_method()
  functions replaced the DSA_set_default_method() and
  DSA_get_default_method() functions respectively, and the DSA_set_method()
  and DSA_new_method() functions were altered to use ENGINEs rather than
  DSA_METHODs during development of OpenSSL 0.9.6.

SEE ALSO
  Functions: dsa(3), DSA_new(3)

Index for Section 3

Alphabetical listing for D

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