Merge branch 'vendor/OPENSSL'
[dragonfly.git] / secure / lib / libcrypto / man / DSA_set_method.3
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129.\" ========================================================================
130.\"
131.IX Title "DSA_set_method 3"
18ed9402 132.TH DSA_set_method 3 "2008-09-27" "0.9.8i" "OpenSSL"
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133.SH "NAME"
134DSA_set_default_method, DSA_get_default_method,
74dab6c2 135DSA_set_method, DSA_new_method, DSA_OpenSSL \- select DSA method
984263bc 136.SH "SYNOPSIS"
8b0cefbb 137.IX Header "SYNOPSIS"
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138.Vb 2
139\& #include <openssl/dsa.h>
140\& #include <openssl/engine.h>
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141.Ve
142.PP
143.Vb 1
984263bc 144\& void DSA_set_default_method(const DSA_METHOD *meth);
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145.Ve
146.PP
147.Vb 1
984263bc 148\& const DSA_METHOD *DSA_get_default_method(void);
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149.Ve
150.PP
151.Vb 1
984263bc 152\& int DSA_set_method(DSA *dsa, const DSA_METHOD *meth);
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153.Ve
154.PP
155.Vb 1
984263bc 156\& DSA *DSA_new_method(ENGINE *engine);
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157.Ve
158.PP
159.Vb 1
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160\& DSA_METHOD *DSA_OpenSSL(void);
161.Ve
162.SH "DESCRIPTION"
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163.IX Header "DESCRIPTION"
164A \fB\s-1DSA_METHOD\s0\fR specifies the functions that OpenSSL uses for \s-1DSA\s0
984263bc 165operations. By modifying the method, alternative implementations
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166such as hardware accelerators may be used. \s-1IMPORTANT:\s0 See the \s-1NOTES\s0 section for
167important information about how these \s-1DSA\s0 \s-1API\s0 functions are affected by the use
168of \fB\s-1ENGINE\s0\fR \s-1API\s0 calls.
984263bc 169.PP
8b0cefbb 170Initially, the default \s-1DSA_METHOD\s0 is the OpenSSL internal implementation,
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171as returned by \fIDSA_OpenSSL()\fR.
172.PP
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173\&\fIDSA_set_default_method()\fR makes \fBmeth\fR the default method for all \s-1DSA\s0
174structures created later. \fB\s-1NB\s0\fR: This is true only whilst no \s-1ENGINE\s0 has
175been set as a default for \s-1DSA\s0, so this function is no longer recommended.
984263bc 176.PP
8b0cefbb 177\&\fIDSA_get_default_method()\fR returns a pointer to the current default
aac4ff6f 178\&\s-1DSA_METHOD\s0. However, the meaningfulness of this result is dependent on
8b0cefbb 179whether the \s-1ENGINE\s0 \s-1API\s0 is being used, so this function is no longer
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180recommended.
181.PP
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182\&\fIDSA_set_method()\fR selects \fBmeth\fR to perform all operations using the key
183\&\fBrsa\fR. This will replace the \s-1DSA_METHOD\s0 used by the \s-1DSA\s0 key and if the
184previous method was supplied by an \s-1ENGINE\s0, the handle to that \s-1ENGINE\s0 will
185be released during the change. It is possible to have \s-1DSA\s0 keys that only
186work with certain \s-1DSA_METHOD\s0 implementations (eg. from an \s-1ENGINE\s0 module
984263bc 187that supports embedded hardware-protected keys), and in such cases
8b0cefbb 188attempting to change the \s-1DSA_METHOD\s0 for the key can have unexpected
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189results.
190.PP
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191\&\fIDSA_new_method()\fR allocates and initializes a \s-1DSA\s0 structure so that \fBengine\fR
192will be used for the \s-1DSA\s0 operations. If \fBengine\fR is \s-1NULL\s0, the default engine
193for \s-1DSA\s0 operations is used, and if no default \s-1ENGINE\s0 is set, the \s-1DSA_METHOD\s0
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194controlled by \fIDSA_set_default_method()\fR is used.
195.SH "THE DSA_METHOD STRUCTURE"
8b0cefbb 196.IX Header "THE DSA_METHOD STRUCTURE"
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197struct
198 {
199 /* name of the implementation */
200 const char *name;
201.PP
202.Vb 3
203\& /* sign */
204\& DSA_SIG *(*dsa_do_sign)(const unsigned char *dgst, int dlen,
205\& DSA *dsa);
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206.Ve
207.PP
208.Vb 3
209\& /* pre-compute k^-1 and r */
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210\& int (*dsa_sign_setup)(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
211\& BIGNUM **rp);
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212.Ve
213.PP
214.Vb 3
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215\& /* verify */
216\& int (*dsa_do_verify)(const unsigned char *dgst, int dgst_len,
217\& DSA_SIG *sig, DSA *dsa);
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218.Ve
219.PP
220.Vb 5
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221\& /* compute rr = a1^p1 * a2^p2 mod m (May be NULL for some
222\& implementations) */
223\& int (*dsa_mod_exp)(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1,
224\& BIGNUM *a2, BIGNUM *p2, BIGNUM *m,
225\& BN_CTX *ctx, BN_MONT_CTX *in_mont);
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226.Ve
227.PP
228.Vb 4
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229\& /* compute r = a ^ p mod m (May be NULL for some implementations) */
230\& int (*bn_mod_exp)(DSA *dsa, BIGNUM *r, BIGNUM *a,
231\& const BIGNUM *p, const BIGNUM *m,
232\& BN_CTX *ctx, BN_MONT_CTX *m_ctx);
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233.Ve
234.PP
235.Vb 2
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236\& /* called at DSA_new */
237\& int (*init)(DSA *DSA);
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238.Ve
239.PP
240.Vb 2
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241\& /* called at DSA_free */
242\& int (*finish)(DSA *DSA);
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243.Ve
244.PP
245.Vb 1
984263bc 246\& int flags;
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247.Ve
248.PP
249.Vb 1
984263bc 250\& char *app_data; /* ?? */
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251.Ve
252.PP
253.Vb 1
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254\& } DSA_METHOD;
255.Ve
256.SH "RETURN VALUES"
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257.IX Header "RETURN VALUES"
258\&\fIDSA_OpenSSL()\fR and \fIDSA_get_default_method()\fR return pointers to the respective
259\&\fB\s-1DSA_METHOD\s0\fRs.
984263bc 260.PP
8b0cefbb 261\&\fIDSA_set_default_method()\fR returns no value.
984263bc 262.PP
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263\&\fIDSA_set_method()\fR returns non-zero if the provided \fBmeth\fR was successfully set as
264the method for \fBdsa\fR (including unloading the \s-1ENGINE\s0 handle if the previous
265method was supplied by an \s-1ENGINE\s0).
984263bc 266.PP
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267\&\fIDSA_new_method()\fR returns \s-1NULL\s0 and sets an error code that can be
268obtained by \fIERR_get_error\fR\|(3) if the allocation
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269fails. Otherwise it returns a pointer to the newly allocated structure.
270.SH "NOTES"
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271.IX Header "NOTES"
272As of version 0.9.7, \s-1DSA_METHOD\s0 implementations are grouped together with other
273algorithmic APIs (eg. \s-1RSA_METHOD\s0, \s-1EVP_CIPHER\s0, etc) in \fB\s-1ENGINE\s0\fR modules. If a
274default \s-1ENGINE\s0 is specified for \s-1DSA\s0 functionality using an \s-1ENGINE\s0 \s-1API\s0 function,
275that will override any \s-1DSA\s0 defaults set using the \s-1DSA\s0 \s-1API\s0 (ie.
276\&\fIDSA_set_default_method()\fR). For this reason, the \s-1ENGINE\s0 \s-1API\s0 is the recommended way
277to control default implementations for use in \s-1DSA\s0 and other cryptographic
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278algorithms.
279.SH "SEE ALSO"
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280.IX Header "SEE ALSO"
281\&\fIdsa\fR\|(3), \fIDSA_new\fR\|(3)
984263bc 282.SH "HISTORY"
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283.IX Header "HISTORY"
284\&\fIDSA_set_default_method()\fR, \fIDSA_get_default_method()\fR, \fIDSA_set_method()\fR,
285\&\fIDSA_new_method()\fR and \fIDSA_OpenSSL()\fR were added in OpenSSL 0.9.4.
984263bc 286.PP
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287\&\fIDSA_set_default_openssl_method()\fR and \fIDSA_get_default_openssl_method()\fR replaced
288\&\fIDSA_set_default_method()\fR and \fIDSA_get_default_method()\fR respectively, and
289\&\fIDSA_set_method()\fR and \fIDSA_new_method()\fR were altered to use \fB\s-1ENGINE\s0\fRs rather than
290\&\fB\s-1DSA_METHOD\s0\fRs during development of the engine version of OpenSSL 0.9.6. For
2910.9.7, the handling of defaults in the \s-1ENGINE\s0 \s-1API\s0 was restructured so that this
984263bc 292change was reversed, and behaviour of the other functions resembled more closely
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293the previous behaviour. The behaviour of defaults in the \s-1ENGINE\s0 \s-1API\s0 now
294transparently overrides the behaviour of defaults in the \s-1DSA\s0 \s-1API\s0 without
984263bc 295requiring changing these function prototypes.