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91 .tm Index:\\$1\t\\n%\t"\\$2"
96 .TH DSA_set_method 3 "0.9.7d" "2/Sep/2004" "OpenSSL"
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191 DSA_set_default_method, DSA_get_default_method,
192 DSA_set_method, DSA_new_method, DSA_OpenSSL \- select DSA method
196 \& #include <openssl/dsa.h>
197 \& #include <openssl/engine.h>
200 \& void DSA_set_default_method(const DSA_METHOD *meth);
203 \& const DSA_METHOD *DSA_get_default_method(void);
206 \& int DSA_set_method(DSA *dsa, const DSA_METHOD *meth);
209 \& DSA *DSA_new_method(ENGINE *engine);
212 \& DSA_METHOD *DSA_OpenSSL(void);
215 A \fBDSA_METHOD\fR specifies the functions that OpenSSL uses for DSA
216 operations. By modifying the method, alternative implementations
217 such as hardware accelerators may be used. IMPORTANT: See the NOTES section for
218 important information about how these DSA API functions are affected by the use
219 of \fBENGINE\fR API calls.
221 Initially, the default DSA_METHOD is the OpenSSL internal implementation,
222 as returned by \fIDSA_OpenSSL()\fR.
224 \fIDSA_set_default_method()\fR makes \fBmeth\fR the default method for all DSA
225 structures created later. \fBNB\fR: This is true only whilst no ENGINE has
226 been set as a default for DSA, so this function is no longer recommended.
228 \fIDSA_get_default_method()\fR returns a pointer to the current default
229 DSA_METHOD. However, the meaningfulness of this result is dependant on
230 whether the ENGINE API is being used, so this function is no longer
233 \fIDSA_set_method()\fR selects \fBmeth\fR to perform all operations using the key
234 \fBrsa\fR. This will replace the DSA_METHOD used by the DSA key and if the
235 previous method was supplied by an ENGINE, the handle to that ENGINE will
236 be released during the change. It is possible to have DSA keys that only
237 work with certain DSA_METHOD implementations (eg. from an ENGINE module
238 that supports embedded hardware-protected keys), and in such cases
239 attempting to change the DSA_METHOD for the key can have unexpected
242 \fIDSA_new_method()\fR allocates and initializes a DSA structure so that \fBengine\fR
243 will be used for the DSA operations. If \fBengine\fR is NULL, the default engine
244 for DSA operations is used, and if no default ENGINE is set, the DSA_METHOD
245 controlled by \fIDSA_set_default_method()\fR is used.
246 .SH "THE DSA_METHOD STRUCTURE"
249 /* name of the implementation */
254 \& DSA_SIG *(*dsa_do_sign)(const unsigned char *dgst, int dlen,
258 \& /* pre-compute k^-1 and r */
259 \& int (*dsa_sign_setup)(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
264 \& int (*dsa_do_verify)(const unsigned char *dgst, int dgst_len,
265 \& DSA_SIG *sig, DSA *dsa);
268 \& /* compute rr = a1^p1 * a2^p2 mod m (May be NULL for some
269 \& implementations) */
270 \& int (*dsa_mod_exp)(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1,
271 \& BIGNUM *a2, BIGNUM *p2, BIGNUM *m,
272 \& BN_CTX *ctx, BN_MONT_CTX *in_mont);
275 \& /* compute r = a ^ p mod m (May be NULL for some implementations) */
276 \& int (*bn_mod_exp)(DSA *dsa, BIGNUM *r, BIGNUM *a,
277 \& const BIGNUM *p, const BIGNUM *m,
278 \& BN_CTX *ctx, BN_MONT_CTX *m_ctx);
281 \& /* called at DSA_new */
282 \& int (*init)(DSA *DSA);
285 \& /* called at DSA_free */
286 \& int (*finish)(DSA *DSA);
292 \& char *app_data; /* ?? */
298 \fIDSA_OpenSSL()\fR and \fIDSA_get_default_method()\fR return pointers to the respective
301 \fIDSA_set_default_method()\fR returns no value.
303 \fIDSA_set_method()\fR returns non-zero if the provided \fBmeth\fR was successfully set as
304 the method for \fBdsa\fR (including unloading the ENGINE handle if the previous
305 method was supplied by an ENGINE).
307 \fIDSA_new_method()\fR returns NULL and sets an error code that can be
308 obtained by ERR_get_error(3) if the allocation
309 fails. Otherwise it returns a pointer to the newly allocated structure.
311 As of version 0.9.7, DSA_METHOD implementations are grouped together with other
312 algorithmic APIs (eg. RSA_METHOD, EVP_CIPHER, etc) in \fBENGINE\fR modules. If a
313 default ENGINE is specified for DSA functionality using an ENGINE API function,
314 that will override any DSA defaults set using the DSA API (ie.
315 \fIDSA_set_default_method()\fR). For this reason, the ENGINE API is the recommended way
316 to control default implementations for use in DSA and other cryptographic
321 \fIDSA_set_default_method()\fR, \fIDSA_get_default_method()\fR, \fIDSA_set_method()\fR,
322 \fIDSA_new_method()\fR and \fIDSA_OpenSSL()\fR were added in OpenSSL 0.9.4.
324 \fIDSA_set_default_openssl_method()\fR and \fIDSA_get_default_openssl_method()\fR replaced
325 \fIDSA_set_default_method()\fR and \fIDSA_get_default_method()\fR respectively, and
326 \fIDSA_set_method()\fR and \fIDSA_new_method()\fR were altered to use \fBENGINE\fRs rather than
327 \fBDSA_METHOD\fRs during development of the engine version of OpenSSL 0.9.6. For
328 0.9.7, the handling of defaults in the ENGINE API was restructured so that this
329 change was reversed, and behaviour of the other functions resembled more closely
330 the previous behaviour. The behaviour of defaults in the ENGINE API now
331 transparently overrides the behaviour of defaults in the DSA API without
332 requiring changing these function prototypes.
335 .IX Title "DSA_set_method 3"
336 .IX Name "DSA_set_default_method, DSA_get_default_method,
337 DSA_set_method, DSA_new_method, DSA_OpenSSL - select DSA method"
341 .IX Header "SYNOPSIS"
343 .IX Header "DESCRIPTION"
345 .IX Header "THE DSA_METHOD STRUCTURE"
347 .IX Header "RETURN VALUES"
351 .IX Header "SEE ALSO"