Regenerate the manual pages after the OpenSSL update to 0.9.7e.
[dragonfly.git] / secure / lib / libcrypto / man / DH_set_method.3
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129.\" ========================================================================
130.\"
131.IX Title "DH_set_method 3"
132.TH DH_set_method 3 "2004-12-18" "0.9.7e" "OpenSSL"
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133.SH "NAME"
134DH_set_default_method, DH_get_default_method,
74dab6c2 135DH_set_method, DH_new_method, DH_OpenSSL \- select DH method
984263bc 136.SH "SYNOPSIS"
8b0cefbb 137.IX Header "SYNOPSIS"
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138.Vb 2
139\& #include <openssl/dh.h>
140\& #include <openssl/engine.h>
141.Ve
8b0cefbb 142.PP
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143.Vb 1
144\& void DH_set_default_method(const DH_METHOD *meth);
145.Ve
8b0cefbb 146.PP
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147.Vb 1
148\& const DH_METHOD *DH_get_default_method(void);
149.Ve
8b0cefbb 150.PP
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151.Vb 1
152\& int DH_set_method(DH *dh, const DH_METHOD *meth);
153.Ve
8b0cefbb 154.PP
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155.Vb 1
156\& DH *DH_new_method(ENGINE *engine);
157.Ve
8b0cefbb 158.PP
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159.Vb 1
160\& const DH_METHOD *DH_OpenSSL(void);
161.Ve
162.SH "DESCRIPTION"
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163.IX Header "DESCRIPTION"
164A \fB\s-1DH_METHOD\s0\fR specifies the functions that OpenSSL uses for Diffie-Hellman
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-1DH\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-1DH_METHOD\s0 is the OpenSSL internal implementation, as
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171returned by \fIDH_OpenSSL()\fR.
172.PP
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173\&\fIDH_set_default_method()\fR makes \fBmeth\fR the default method for all \s-1DH\s0
174structures created later. \fB\s-1NB\s0\fR: This is true only whilst no \s-1ENGINE\s0 has been set
175as a default for \s-1DH\s0, so this function is no longer recommended.
984263bc 176.PP
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177\&\fIDH_get_default_method()\fR returns a pointer to the current default \s-1DH_METHOD\s0.
178However, the meaningfulness of this result is dependant on whether the \s-1ENGINE\s0
179\&\s-1API\s0 is being used, so this function is no longer recommended.
984263bc 180.PP
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181\&\fIDH_set_method()\fR selects \fBmeth\fR to perform all operations using the key \fBdh\fR.
182This will replace the \s-1DH_METHOD\s0 used by the \s-1DH\s0 key and if the previous method
183was supplied by an \s-1ENGINE\s0, the handle to that \s-1ENGINE\s0 will be released during the
184change. It is possible to have \s-1DH\s0 keys that only work with certain \s-1DH_METHOD\s0
185implementations (eg. from an \s-1ENGINE\s0 module that supports embedded
186hardware-protected keys), and in such cases attempting to change the \s-1DH_METHOD\s0
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187for the key can have unexpected results.
188.PP
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189\&\fIDH_new_method()\fR allocates and initializes a \s-1DH\s0 structure so that \fBengine\fR will
190be used for the \s-1DH\s0 operations. If \fBengine\fR is \s-1NULL\s0, the default \s-1ENGINE\s0 for \s-1DH\s0
191operations is used, and if no default \s-1ENGINE\s0 is set, the \s-1DH_METHOD\s0 controlled by
192\&\fIDH_set_default_method()\fR is used.
984263bc 193.SH "THE DH_METHOD STRUCTURE"
8b0cefbb 194.IX Header "THE DH_METHOD STRUCTURE"
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195.Vb 4
196\& typedef struct dh_meth_st
197\& {
198\& /* name of the implementation */
199\& const char *name;
200.Ve
8b0cefbb 201.PP
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202.Vb 2
203\& /* generate private and public DH values for key agreement */
204\& int (*generate_key)(DH *dh);
205.Ve
8b0cefbb 206.PP
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207.Vb 2
208\& /* compute shared secret */
209\& int (*compute_key)(unsigned char *key, BIGNUM *pub_key, DH *dh);
210.Ve
8b0cefbb 211.PP
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212.Vb 4
213\& /* compute r = a ^ p mod m (May be NULL for some implementations) */
214\& int (*bn_mod_exp)(DH *dh, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
215\& const BIGNUM *m, BN_CTX *ctx,
216\& BN_MONT_CTX *m_ctx);
217.Ve
8b0cefbb 218.PP
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219.Vb 2
220\& /* called at DH_new */
221\& int (*init)(DH *dh);
222.Ve
8b0cefbb 223.PP
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224.Vb 2
225\& /* called at DH_free */
226\& int (*finish)(DH *dh);
227.Ve
8b0cefbb 228.PP
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229.Vb 1
230\& int flags;
231.Ve
8b0cefbb 232.PP
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233.Vb 1
234\& char *app_data; /* ?? */
235.Ve
8b0cefbb 236.PP
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237.Vb 1
238\& } DH_METHOD;
239.Ve
240.SH "RETURN VALUES"
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241.IX Header "RETURN VALUES"
242\&\fIDH_OpenSSL()\fR and \fIDH_get_default_method()\fR return pointers to the respective
243\&\fB\s-1DH_METHOD\s0\fRs.
984263bc 244.PP
8b0cefbb 245\&\fIDH_set_default_method()\fR returns no value.
984263bc 246.PP
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247\&\fIDH_set_method()\fR returns non-zero if the provided \fBmeth\fR was successfully set as
248the method for \fBdh\fR (including unloading the \s-1ENGINE\s0 handle if the previous
249method was supplied by an \s-1ENGINE\s0).
984263bc 250.PP
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251\&\fIDH_new_method()\fR returns \s-1NULL\s0 and sets an error code that can be obtained by
252\&\fIERR_get_error\fR\|(3) if the allocation fails. Otherwise it
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253returns a pointer to the newly allocated structure.
254.SH "NOTES"
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255.IX Header "NOTES"
256As of version 0.9.7, \s-1DH_METHOD\s0 implementations are grouped together with other
257algorithmic APIs (eg. \s-1RSA_METHOD\s0, \s-1EVP_CIPHER\s0, etc) in \fB\s-1ENGINE\s0\fR modules. If a
258default \s-1ENGINE\s0 is specified for \s-1DH\s0 functionality using an \s-1ENGINE\s0 \s-1API\s0 function,
259that will override any \s-1DH\s0 defaults set using the \s-1DH\s0 \s-1API\s0 (ie.
260\&\fIDH_set_default_method()\fR). For this reason, the \s-1ENGINE\s0 \s-1API\s0 is the recommended way
261to control default implementations for use in \s-1DH\s0 and other cryptographic
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262algorithms.
263.SH "SEE ALSO"
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264.IX Header "SEE ALSO"
265\&\fIdh\fR\|(3), \fIDH_new\fR\|(3)
984263bc 266.SH "HISTORY"
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267.IX Header "HISTORY"
268\&\fIDH_set_default_method()\fR, \fIDH_get_default_method()\fR, \fIDH_set_method()\fR,
269\&\fIDH_new_method()\fR and \fIDH_OpenSSL()\fR were added in OpenSSL 0.9.4.
984263bc 270.PP
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271\&\fIDH_set_default_openssl_method()\fR and \fIDH_get_default_openssl_method()\fR replaced
272\&\fIDH_set_default_method()\fR and \fIDH_get_default_method()\fR respectively, and
273\&\fIDH_set_method()\fR and \fIDH_new_method()\fR were altered to use \fB\s-1ENGINE\s0\fRs rather than
274\&\fB\s-1DH_METHOD\s0\fRs during development of the engine version of OpenSSL 0.9.6. For
2750.9.7, the handling of defaults in the \s-1ENGINE\s0 \s-1API\s0 was restructured so that this
984263bc 276change was reversed, and behaviour of the other functions resembled more closely
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277the previous behaviour. The behaviour of defaults in the \s-1ENGINE\s0 \s-1API\s0 now
278transparently overrides the behaviour of defaults in the \s-1DH\s0 \s-1API\s0 without
984263bc 279requiring changing these function prototypes.