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135 .IX Title "DSA_set_method 3"
136 .TH DSA_set_method 3 "2016-09-22" "1.0.2i" "OpenSSL"
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142 DSA_set_default_method, DSA_get_default_method,
143 DSA_set_method, DSA_new_method, DSA_OpenSSL \- select DSA method
145 .IX Header "SYNOPSIS"
147 \& #include <openssl/dsa.h>
148 \& #include <openssl/engine.h>
150 \& void DSA_set_default_method(const DSA_METHOD *meth);
152 \& const DSA_METHOD *DSA_get_default_method(void);
154 \& int DSA_set_method(DSA *dsa, const DSA_METHOD *meth);
156 \& DSA *DSA_new_method(ENGINE *engine);
158 \& DSA_METHOD *DSA_OpenSSL(void);
161 .IX Header "DESCRIPTION"
162 A \fB\s-1DSA_METHOD\s0\fR specifies the functions that OpenSSL uses for \s-1DSA\s0
163 operations. By modifying the method, alternative implementations
164 such as hardware accelerators may be used. \s-1IMPORTANT:\s0 See the \s-1NOTES\s0 section for
165 important information about how these \s-1DSA API\s0 functions are affected by the use
166 of \fB\s-1ENGINE\s0\fR \s-1API\s0 calls.
168 Initially, the default \s-1DSA_METHOD\s0 is the OpenSSL internal implementation,
169 as returned by \fIDSA_OpenSSL()\fR.
171 \&\fIDSA_set_default_method()\fR makes \fBmeth\fR the default method for all \s-1DSA\s0
172 structures created later. \fB\s-1NB\s0\fR: This is true only whilst no \s-1ENGINE\s0 has
173 been set as a default for \s-1DSA,\s0 so this function is no longer recommended.
175 \&\fIDSA_get_default_method()\fR returns a pointer to the current default
176 \&\s-1DSA_METHOD.\s0 However, the meaningfulness of this result is dependent on
177 whether the \s-1ENGINE API\s0 is being used, so this function is no longer
180 \&\fIDSA_set_method()\fR selects \fBmeth\fR to perform all operations using the key
181 \&\fBrsa\fR. This will replace the \s-1DSA_METHOD\s0 used by the \s-1DSA\s0 key and if the
182 previous method was supplied by an \s-1ENGINE,\s0 the handle to that \s-1ENGINE\s0 will
183 be released during the change. It is possible to have \s-1DSA\s0 keys that only
184 work with certain \s-1DSA_METHOD\s0 implementations (eg. from an \s-1ENGINE\s0 module
185 that supports embedded hardware-protected keys), and in such cases
186 attempting to change the \s-1DSA_METHOD\s0 for the key can have unexpected
189 \&\fIDSA_new_method()\fR allocates and initializes a \s-1DSA\s0 structure so that \fBengine\fR
190 will be used for the \s-1DSA\s0 operations. If \fBengine\fR is \s-1NULL,\s0 the default engine
191 for \s-1DSA\s0 operations is used, and if no default \s-1ENGINE\s0 is set, the \s-1DSA_METHOD\s0
192 controlled by \fIDSA_set_default_method()\fR is used.
193 .SH "THE DSA_METHOD STRUCTURE"
194 .IX Header "THE DSA_METHOD STRUCTURE"
197 /* name of the implementation */
202 \& DSA_SIG *(*dsa_do_sign)(const unsigned char *dgst, int dlen,
205 \& /* pre\-compute k^\-1 and r */
206 \& int (*dsa_sign_setup)(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
210 \& int (*dsa_do_verify)(const unsigned char *dgst, int dgst_len,
211 \& DSA_SIG *sig, DSA *dsa);
213 \& /* compute rr = a1^p1 * a2^p2 mod m (May be NULL for some
214 \& implementations) */
215 \& int (*dsa_mod_exp)(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1,
216 \& BIGNUM *a2, BIGNUM *p2, BIGNUM *m,
217 \& BN_CTX *ctx, BN_MONT_CTX *in_mont);
219 \& /* compute r = a ^ p mod m (May be NULL for some implementations) */
220 \& int (*bn_mod_exp)(DSA *dsa, BIGNUM *r, BIGNUM *a,
221 \& const BIGNUM *p, const BIGNUM *m,
222 \& BN_CTX *ctx, BN_MONT_CTX *m_ctx);
224 \& /* called at DSA_new */
225 \& int (*init)(DSA *DSA);
227 \& /* called at DSA_free */
228 \& int (*finish)(DSA *DSA);
232 \& char *app_data; /* ?? */
237 .IX Header "RETURN VALUES"
238 \&\fIDSA_OpenSSL()\fR and \fIDSA_get_default_method()\fR return pointers to the respective
239 \&\fB\s-1DSA_METHOD\s0\fRs.
241 \&\fIDSA_set_default_method()\fR returns no value.
243 \&\fIDSA_set_method()\fR returns non-zero if the provided \fBmeth\fR was successfully set as
244 the method for \fBdsa\fR (including unloading the \s-1ENGINE\s0 handle if the previous
245 method was supplied by an \s-1ENGINE\s0).
247 \&\fIDSA_new_method()\fR returns \s-1NULL\s0 and sets an error code that can be
248 obtained by \fIERR_get_error\fR\|(3) if the allocation
249 fails. Otherwise it returns a pointer to the newly allocated structure.
252 As of version 0.9.7, \s-1DSA_METHOD\s0 implementations are grouped together with other
253 algorithmic APIs (eg. \s-1RSA_METHOD, EVP_CIPHER,\s0 etc) in \fB\s-1ENGINE\s0\fR modules. If a
254 default \s-1ENGINE\s0 is specified for \s-1DSA\s0 functionality using an \s-1ENGINE API\s0 function,
255 that will override any \s-1DSA\s0 defaults set using the \s-1DSA API \s0(ie.
256 \&\fIDSA_set_default_method()\fR). For this reason, the \s-1ENGINE API\s0 is the recommended way
257 to control default implementations for use in \s-1DSA\s0 and other cryptographic
260 .IX Header "SEE ALSO"
261 \&\fIdsa\fR\|(3), \fIDSA_new\fR\|(3)
264 \&\fIDSA_set_default_method()\fR, \fIDSA_get_default_method()\fR, \fIDSA_set_method()\fR,
265 \&\fIDSA_new_method()\fR and \fIDSA_OpenSSL()\fR were added in OpenSSL 0.9.4.
267 \&\fIDSA_set_default_openssl_method()\fR and \fIDSA_get_default_openssl_method()\fR replaced
268 \&\fIDSA_set_default_method()\fR and \fIDSA_get_default_method()\fR respectively, and
269 \&\fIDSA_set_method()\fR and \fIDSA_new_method()\fR were altered to use \fB\s-1ENGINE\s0\fRs rather than
270 \&\fB\s-1DSA_METHOD\s0\fRs during development of the engine version of OpenSSL 0.9.6. For
271 0.9.7, the handling of defaults in the \s-1ENGINE API\s0 was restructured so that this
272 change was reversed, and behaviour of the other functions resembled more closely
273 the previous behaviour. The behaviour of defaults in the \s-1ENGINE API\s0 now
274 transparently overrides the behaviour of defaults in the \s-1DSA API\s0 without
275 requiring changing these function prototypes.