Merge from vendor branch OPENSSL:
[dragonfly.git] / secure / lib / libcrypto / man / DSA_set_method.3
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124.\" ========================================================================
125.\"
126.IX Title "DSA_set_method 3"
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127.TH DSA_set_method 3 "2007-10-24" "0.9.8g" "OpenSSL"
128.\" For nroff, turn off justification. Always turn off hyphenation; it makes
129.\" way too many mistakes in technical documents.
130.if n .ad l
131.nh
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132.SH "NAME"
133DSA_set_default_method, DSA_get_default_method,
74dab6c2 134DSA_set_method, DSA_new_method, DSA_OpenSSL \- select DSA method
984263bc 135.SH "SYNOPSIS"
8b0cefbb 136.IX Header "SYNOPSIS"
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137.Vb 2
138\& #include <openssl/dsa.h>
139\& #include <openssl/engine.h>
2eaa1526 140\&
984263bc 141\& void DSA_set_default_method(const DSA_METHOD *meth);
2eaa1526 142\&
984263bc 143\& const DSA_METHOD *DSA_get_default_method(void);
2eaa1526 144\&
984263bc 145\& int DSA_set_method(DSA *dsa, const DSA_METHOD *meth);
2eaa1526 146\&
984263bc 147\& DSA *DSA_new_method(ENGINE *engine);
2eaa1526 148\&
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149\& DSA_METHOD *DSA_OpenSSL(void);
150.Ve
151.SH "DESCRIPTION"
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152.IX Header "DESCRIPTION"
153A \fB\s-1DSA_METHOD\s0\fR specifies the functions that OpenSSL uses for \s-1DSA\s0
984263bc 154operations. By modifying the method, alternative implementations
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155such as hardware accelerators may be used. \s-1IMPORTANT:\s0 See the \s-1NOTES\s0 section for
156important information about how these \s-1DSA\s0 \s-1API\s0 functions are affected by the use
157of \fB\s-1ENGINE\s0\fR \s-1API\s0 calls.
984263bc 158.PP
8b0cefbb 159Initially, the default \s-1DSA_METHOD\s0 is the OpenSSL internal implementation,
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160as returned by \fIDSA_OpenSSL()\fR.
161.PP
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162\&\fIDSA_set_default_method()\fR makes \fBmeth\fR the default method for all \s-1DSA\s0
163structures created later. \fB\s-1NB\s0\fR: This is true only whilst no \s-1ENGINE\s0 has
164been set as a default for \s-1DSA\s0, so this function is no longer recommended.
984263bc 165.PP
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166\&\fIDSA_get_default_method()\fR returns a pointer to the current default
167\&\s-1DSA_METHOD\s0. However, the meaningfulness of this result is dependant on
168whether the \s-1ENGINE\s0 \s-1API\s0 is being used, so this function is no longer
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169recommended.
170.PP
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171\&\fIDSA_set_method()\fR selects \fBmeth\fR to perform all operations using the key
172\&\fBrsa\fR. This will replace the \s-1DSA_METHOD\s0 used by the \s-1DSA\s0 key and if the
173previous method was supplied by an \s-1ENGINE\s0, the handle to that \s-1ENGINE\s0 will
174be released during the change. It is possible to have \s-1DSA\s0 keys that only
175work with certain \s-1DSA_METHOD\s0 implementations (eg. from an \s-1ENGINE\s0 module
984263bc 176that supports embedded hardware-protected keys), and in such cases
8b0cefbb 177attempting to change the \s-1DSA_METHOD\s0 for the key can have unexpected
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178results.
179.PP
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180\&\fIDSA_new_method()\fR allocates and initializes a \s-1DSA\s0 structure so that \fBengine\fR
181will be used for the \s-1DSA\s0 operations. If \fBengine\fR is \s-1NULL\s0, the default engine
182for \s-1DSA\s0 operations is used, and if no default \s-1ENGINE\s0 is set, the \s-1DSA_METHOD\s0
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183controlled by \fIDSA_set_default_method()\fR is used.
184.SH "THE DSA_METHOD STRUCTURE"
8b0cefbb 185.IX Header "THE DSA_METHOD STRUCTURE"
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186struct
187 {
188 /* name of the implementation */
189 const char *name;
190.PP
191.Vb 3
192\& /* sign */
193\& DSA_SIG *(*dsa_do_sign)(const unsigned char *dgst, int dlen,
194\& DSA *dsa);
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195\&
196\& /* pre\-compute k^\-1 and r */
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197\& int (*dsa_sign_setup)(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
198\& BIGNUM **rp);
2eaa1526 199\&
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200\& /* verify */
201\& int (*dsa_do_verify)(const unsigned char *dgst, int dgst_len,
202\& DSA_SIG *sig, DSA *dsa);
2eaa1526 203\&
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204\& /* compute rr = a1^p1 * a2^p2 mod m (May be NULL for some
205\& implementations) */
206\& int (*dsa_mod_exp)(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1,
207\& BIGNUM *a2, BIGNUM *p2, BIGNUM *m,
208\& BN_CTX *ctx, BN_MONT_CTX *in_mont);
2eaa1526 209\&
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210\& /* compute r = a ^ p mod m (May be NULL for some implementations) */
211\& int (*bn_mod_exp)(DSA *dsa, BIGNUM *r, BIGNUM *a,
212\& const BIGNUM *p, const BIGNUM *m,
213\& BN_CTX *ctx, BN_MONT_CTX *m_ctx);
2eaa1526 214\&
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215\& /* called at DSA_new */
216\& int (*init)(DSA *DSA);
2eaa1526 217\&
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218\& /* called at DSA_free */
219\& int (*finish)(DSA *DSA);
2eaa1526 220\&
984263bc 221\& int flags;
2eaa1526 222\&
984263bc 223\& char *app_data; /* ?? */
2eaa1526 224\&
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225\& } DSA_METHOD;
226.Ve
227.SH "RETURN VALUES"
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228.IX Header "RETURN VALUES"
229\&\fIDSA_OpenSSL()\fR and \fIDSA_get_default_method()\fR return pointers to the respective
230\&\fB\s-1DSA_METHOD\s0\fRs.
984263bc 231.PP
8b0cefbb 232\&\fIDSA_set_default_method()\fR returns no value.
984263bc 233.PP
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234\&\fIDSA_set_method()\fR returns non-zero if the provided \fBmeth\fR was successfully set as
235the method for \fBdsa\fR (including unloading the \s-1ENGINE\s0 handle if the previous
236method was supplied by an \s-1ENGINE\s0).
984263bc 237.PP
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238\&\fIDSA_new_method()\fR returns \s-1NULL\s0 and sets an error code that can be
239obtained by \fIERR_get_error\fR\|(3) if the allocation
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240fails. Otherwise it returns a pointer to the newly allocated structure.
241.SH "NOTES"
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242.IX Header "NOTES"
243As of version 0.9.7, \s-1DSA_METHOD\s0 implementations are grouped together with other
244algorithmic APIs (eg. \s-1RSA_METHOD\s0, \s-1EVP_CIPHER\s0, etc) in \fB\s-1ENGINE\s0\fR modules. If a
245default \s-1ENGINE\s0 is specified for \s-1DSA\s0 functionality using an \s-1ENGINE\s0 \s-1API\s0 function,
246that will override any \s-1DSA\s0 defaults set using the \s-1DSA\s0 \s-1API\s0 (ie.
247\&\fIDSA_set_default_method()\fR). For this reason, the \s-1ENGINE\s0 \s-1API\s0 is the recommended way
248to control default implementations for use in \s-1DSA\s0 and other cryptographic
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249algorithms.
250.SH "SEE ALSO"
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251.IX Header "SEE ALSO"
252\&\fIdsa\fR\|(3), \fIDSA_new\fR\|(3)
984263bc 253.SH "HISTORY"
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254.IX Header "HISTORY"
255\&\fIDSA_set_default_method()\fR, \fIDSA_get_default_method()\fR, \fIDSA_set_method()\fR,
256\&\fIDSA_new_method()\fR and \fIDSA_OpenSSL()\fR were added in OpenSSL 0.9.4.
984263bc 257.PP
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258\&\fIDSA_set_default_openssl_method()\fR and \fIDSA_get_default_openssl_method()\fR replaced
259\&\fIDSA_set_default_method()\fR and \fIDSA_get_default_method()\fR respectively, and
260\&\fIDSA_set_method()\fR and \fIDSA_new_method()\fR were altered to use \fB\s-1ENGINE\s0\fRs rather than
261\&\fB\s-1DSA_METHOD\s0\fRs during development of the engine version of OpenSSL 0.9.6. For
2620.9.7, the handling of defaults in the \s-1ENGINE\s0 \s-1API\s0 was restructured so that this
984263bc 263change was reversed, and behaviour of the other functions resembled more closely
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264the previous behaviour. The behaviour of defaults in the \s-1ENGINE\s0 \s-1API\s0 now
265transparently overrides the behaviour of defaults in the \s-1DSA\s0 \s-1API\s0 without
984263bc 266requiring changing these function prototypes.