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| 138 | .\" ====================================================================== |
| 139 | .\" |
| 140 | .IX Title "DSA_set_method 3" |
| 141 | .TH DSA_set_method 3 "0.9.7a" "2003-02-19" "OpenSSL" |
| 142 | .UC |
| 143 | .SH "NAME" |
| 144 | DSA_set_default_method, DSA_get_default_method, |
| 145 | DSA_set_method, DSA_new_method, DSA_OpenSSL \- select \s-1DSA\s0 method |
| 146 | .SH "SYNOPSIS" |
| 147 | .IX Header "SYNOPSIS" |
| 148 | .Vb 2 |
| 149 | \& #include <openssl/dsa.h> |
| 150 | \& #include <openssl/engine.h> |
| 151 | .Ve |
| 152 | .Vb 1 |
| 153 | \& void DSA_set_default_method(const DSA_METHOD *meth); |
| 154 | .Ve |
| 155 | .Vb 1 |
| 156 | \& const DSA_METHOD *DSA_get_default_method(void); |
| 157 | .Ve |
| 158 | .Vb 1 |
| 159 | \& int DSA_set_method(DSA *dsa, const DSA_METHOD *meth); |
| 160 | .Ve |
| 161 | .Vb 1 |
| 162 | \& DSA *DSA_new_method(ENGINE *engine); |
| 163 | .Ve |
| 164 | .Vb 1 |
| 165 | \& DSA_METHOD *DSA_OpenSSL(void); |
| 166 | .Ve |
| 167 | .SH "DESCRIPTION" |
| 168 | .IX Header "DESCRIPTION" |
| 169 | A \fB\s-1DSA_METHOD\s0\fR specifies the functions that OpenSSL uses for \s-1DSA\s0 |
| 170 | operations. By modifying the method, alternative implementations |
| 171 | such as hardware accelerators may be used. \s-1IMPORTANT:\s0 See the \s-1NOTES\s0 section for |
| 172 | important information about how these \s-1DSA\s0 \s-1API\s0 functions are affected by the use |
| 173 | of \fB\s-1ENGINE\s0\fR \s-1API\s0 calls. |
| 174 | .PP |
| 175 | Initially, the default \s-1DSA_METHOD\s0 is the OpenSSL internal implementation, |
| 176 | as returned by \fIDSA_OpenSSL()\fR. |
| 177 | .PP |
| 178 | \&\fIDSA_set_default_method()\fR makes \fBmeth\fR the default method for all \s-1DSA\s0 |
| 179 | structures created later. \fB\s-1NB\s0\fR: This is true only whilst no \s-1ENGINE\s0 has |
| 180 | been set as a default for \s-1DSA\s0, so this function is no longer recommended. |
| 181 | .PP |
| 182 | \&\fIDSA_get_default_method()\fR returns a pointer to the current default |
| 183 | \&\s-1DSA_METHOD\s0. However, the meaningfulness of this result is dependant on |
| 184 | whether the \s-1ENGINE\s0 \s-1API\s0 is being used, so this function is no longer |
| 185 | recommended. |
| 186 | .PP |
| 187 | \&\fIDSA_set_method()\fR selects \fBmeth\fR to perform all operations using the key |
| 188 | \&\fBrsa\fR. This will replace the \s-1DSA_METHOD\s0 used by the \s-1DSA\s0 key and if the |
| 189 | previous method was supplied by an \s-1ENGINE\s0, the handle to that \s-1ENGINE\s0 will |
| 190 | be released during the change. It is possible to have \s-1DSA\s0 keys that only |
| 191 | work with certain \s-1DSA_METHOD\s0 implementations (eg. from an \s-1ENGINE\s0 module |
| 192 | that supports embedded hardware-protected keys), and in such cases |
| 193 | attempting to change the \s-1DSA_METHOD\s0 for the key can have unexpected |
| 194 | results. |
| 195 | .PP |
| 196 | \&\fIDSA_new_method()\fR allocates and initializes a \s-1DSA\s0 structure so that \fBengine\fR |
| 197 | will be used for the \s-1DSA\s0 operations. If \fBengine\fR is \s-1NULL\s0, the default engine |
| 198 | for \s-1DSA\s0 operations is used, and if no default \s-1ENGINE\s0 is set, the \s-1DSA_METHOD\s0 |
| 199 | controlled by \fIDSA_set_default_method()\fR is used. |
| 200 | .SH "THE DSA_METHOD STRUCTURE" |
| 201 | .IX Header "THE DSA_METHOD STRUCTURE" |
| 202 | struct |
| 203 | { |
| 204 | /* name of the implementation */ |
| 205 | const char *name; |
| 206 | .PP |
| 207 | .Vb 3 |
| 208 | \& /* sign */ |
| 209 | \& DSA_SIG *(*dsa_do_sign)(const unsigned char *dgst, int dlen, |
| 210 | \& DSA *dsa); |
| 211 | .Ve |
| 212 | .Vb 3 |
| 213 | \& /* pre-compute k^-1 and r */ |
| 214 | \& int (*dsa_sign_setup)(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, |
| 215 | \& BIGNUM **rp); |
| 216 | .Ve |
| 217 | .Vb 3 |
| 218 | \& /* verify */ |
| 219 | \& int (*dsa_do_verify)(const unsigned char *dgst, int dgst_len, |
| 220 | \& DSA_SIG *sig, DSA *dsa); |
| 221 | .Ve |
| 222 | .Vb 5 |
| 223 | \& /* compute rr = a1^p1 * a2^p2 mod m (May be NULL for some |
| 224 | \& implementations) */ |
| 225 | \& int (*dsa_mod_exp)(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1, |
| 226 | \& BIGNUM *a2, BIGNUM *p2, BIGNUM *m, |
| 227 | \& BN_CTX *ctx, BN_MONT_CTX *in_mont); |
| 228 | .Ve |
| 229 | .Vb 4 |
| 230 | \& /* compute r = a ^ p mod m (May be NULL for some implementations) */ |
| 231 | \& int (*bn_mod_exp)(DSA *dsa, BIGNUM *r, BIGNUM *a, |
| 232 | \& const BIGNUM *p, const BIGNUM *m, |
| 233 | \& BN_CTX *ctx, BN_MONT_CTX *m_ctx); |
| 234 | .Ve |
| 235 | .Vb 2 |
| 236 | \& /* called at DSA_new */ |
| 237 | \& int (*init)(DSA *DSA); |
| 238 | .Ve |
| 239 | .Vb 2 |
| 240 | \& /* called at DSA_free */ |
| 241 | \& int (*finish)(DSA *DSA); |
| 242 | .Ve |
| 243 | .Vb 1 |
| 244 | \& int flags; |
| 245 | .Ve |
| 246 | .Vb 1 |
| 247 | \& char *app_data; /* ?? */ |
| 248 | .Ve |
| 249 | .Vb 1 |
| 250 | \& } DSA_METHOD; |
| 251 | .Ve |
| 252 | .SH "RETURN VALUES" |
| 253 | .IX Header "RETURN VALUES" |
| 254 | \&\fIDSA_OpenSSL()\fR and \fIDSA_get_default_method()\fR return pointers to the respective |
| 255 | \&\fB\s-1DSA_METHOD\s0\fRs. |
| 256 | .PP |
| 257 | \&\fIDSA_set_default_method()\fR returns no value. |
| 258 | .PP |
| 259 | \&\fIDSA_set_method()\fR returns non-zero if the provided \fBmeth\fR was successfully set as |
| 260 | the method for \fBdsa\fR (including unloading the \s-1ENGINE\s0 handle if the previous |
| 261 | method was supplied by an \s-1ENGINE\s0). |
| 262 | .PP |
| 263 | \&\fIDSA_new_method()\fR returns \s-1NULL\s0 and sets an error code that can be |
| 264 | obtained by ERR_get_error(3) if the allocation |
| 265 | fails. Otherwise it returns a pointer to the newly allocated structure. |
| 266 | .SH "NOTES" |
| 267 | .IX Header "NOTES" |
| 268 | As of version 0.9.7, \s-1DSA_METHOD\s0 implementations are grouped together with other |
| 269 | algorithmic APIs (eg. \s-1RSA_METHOD\s0, \s-1EVP_CIPHER\s0, etc) in \fB\s-1ENGINE\s0\fR modules. If a |
| 270 | default \s-1ENGINE\s0 is specified for \s-1DSA\s0 functionality using an \s-1ENGINE\s0 \s-1API\s0 function, |
| 271 | that will override any \s-1DSA\s0 defaults set using the \s-1DSA\s0 \s-1API\s0 (ie. |
| 272 | \&\fIDSA_set_default_method()\fR). For this reason, the \s-1ENGINE\s0 \s-1API\s0 is the recommended way |
| 273 | to control default implementations for use in \s-1DSA\s0 and other cryptographic |
| 274 | algorithms. |
| 275 | .SH "SEE ALSO" |
| 276 | .IX Header "SEE ALSO" |
| 277 | dsa(3), DSA_new(3) |
| 278 | .SH "HISTORY" |
| 279 | .IX Header "HISTORY" |
| 280 | \&\fIDSA_set_default_method()\fR, \fIDSA_get_default_method()\fR, \fIDSA_set_method()\fR, |
| 281 | \&\fIDSA_new_method()\fR and \fIDSA_OpenSSL()\fR were added in OpenSSL 0.9.4. |
| 282 | .PP |
| 283 | \&\fIDSA_set_default_openssl_method()\fR and \fIDSA_get_default_openssl_method()\fR replaced |
| 284 | \&\fIDSA_set_default_method()\fR and \fIDSA_get_default_method()\fR respectively, and |
| 285 | \&\fIDSA_set_method()\fR and \fIDSA_new_method()\fR were altered to use \fB\s-1ENGINE\s0\fRs rather than |
| 286 | \&\fB\s-1DSA_METHOD\s0\fRs during development of the engine version of OpenSSL 0.9.6. For |
| 287 | 0.9.7, the handling of defaults in the \s-1ENGINE\s0 \s-1API\s0 was restructured so that this |
| 288 | change was reversed, and behaviour of the other functions resembled more closely |
| 289 | the previous behaviour. The behaviour of defaults in the \s-1ENGINE\s0 \s-1API\s0 now |
| 290 | transparently overrides the behaviour of defaults in the \s-1DSA\s0 \s-1API\s0 without |
| 291 | requiring changing these function prototypes. |