3.\"
4.\" Standard preamble:
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9.ne 5
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36.\" double quote, and \*(R" will give a right double quote. | will give a
37.\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used
38.\" to do unbreakable dashes and therefore won't be available. \*(C` and
39.\" \*(C' expand to `' in nroff, nothing in troff, for use with C<>
40.tr \(*W-|\(bv\*(Tr
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58.\"
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60.\" for titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and
61.\" index entries marked with X<> in POD. Of course, you'll have to process
62.\" the output yourself in some meaningful fashion.
63.if \nF \{\
64. de IX
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69.\}
70.\"
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77.\" Fear. Run. Save yourself. No user-serviceable parts.
78.bd B 3
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137.rm #[ #] #H #V #F C
138.\" ======================================================================
139.\"
140.IX Title "DH_set_method 3"
| 3.\"
4.\" Standard preamble:
5.\" ======================================================================
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7.br
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9.ne 5
10.PP
11\fB\\$1\fR
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31
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35.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
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37.\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used
38.\" to do unbreakable dashes and therefore won't be available. \*(C` and
39.\" \*(C' expand to `' in nroff, nothing in troff, for use with C<>
40.tr \(*W-|\(bv\*(Tr
41.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
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45. if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
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56. ds R" ''
57'br\}
58.\"
59.\" If the F register is turned on, we'll generate index entries on stderr
60.\" for titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and
61.\" index entries marked with X<> in POD. Of course, you'll have to process
62.\" the output yourself in some meaningful fashion.
63.if \nF \{\
64. de IX
65. tm Index:\\$1\t\\n%\t"\\$2"
66..
67. nr % 0
68. rr F
69.\}
70.\"
71.\" For nroff, turn off justification. Always turn off hyphenation; it
72.\" makes way too many mistakes in technical documents.
73.hy 0
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76.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
77.\" Fear. Run. Save yourself. No user-serviceable parts.
78.bd B 3
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137.rm #[ #] #H #V #F C
138.\" ======================================================================
139.\"
140.IX Title "DH_set_method 3"
|
142.UC
143.SH "NAME"
144DH_set_default_method, DH_get_default_method,
145DH_set_method, DH_new_method, DH_OpenSSL \- select \s-1DH\s0 method
146.SH "SYNOPSIS"
147.IX Header "SYNOPSIS"
148.Vb 2
149\& #include <openssl/dh.h>
150\& #include <openssl/engine.h>
151.Ve
152.Vb 1
153\& void DH_set_default_method(const DH_METHOD *meth);
154.Ve
155.Vb 1
156\& const DH_METHOD *DH_get_default_method(void);
157.Ve
158.Vb 1
159\& int DH_set_method(DH *dh, const DH_METHOD *meth);
160.Ve
161.Vb 1
162\& DH *DH_new_method(ENGINE *engine);
163.Ve
164.Vb 1
165\& const DH_METHOD *DH_OpenSSL(void);
166.Ve
167.SH "DESCRIPTION"
168.IX Header "DESCRIPTION"
169A \fB\s-1DH_METHOD\s0\fR specifies the functions that OpenSSL uses for Diffie-Hellman
170operations. By modifying the method, alternative implementations
171such as hardware accelerators may be used. \s-1IMPORTANT:\s0 See the \s-1NOTES\s0 section for
172important information about how these \s-1DH\s0 \s-1API\s0 functions are affected by the use
173of \fB\s-1ENGINE\s0\fR \s-1API\s0 calls.
174.PP
175Initially, the default \s-1DH_METHOD\s0 is the OpenSSL internal implementation, as
176returned by \fIDH_OpenSSL()\fR.
177.PP
178\&\fIDH_set_default_method()\fR makes \fBmeth\fR the default method for all \s-1DH\s0
179structures created later. \fB\s-1NB\s0\fR: This is true only whilst no \s-1ENGINE\s0 has been set
180as a default for \s-1DH\s0, so this function is no longer recommended.
181.PP
182\&\fIDH_get_default_method()\fR returns a pointer to the current default \s-1DH_METHOD\s0.
183However, the meaningfulness of this result is dependant on whether the \s-1ENGINE\s0
184\&\s-1API\s0 is being used, so this function is no longer recommended.
185.PP
186\&\fIDH_set_method()\fR selects \fBmeth\fR to perform all operations using the key \fBdh\fR.
187This will replace the \s-1DH_METHOD\s0 used by the \s-1DH\s0 key and if the previous method
188was supplied by an \s-1ENGINE\s0, the handle to that \s-1ENGINE\s0 will be released during the
189change. It is possible to have \s-1DH\s0 keys that only work with certain \s-1DH_METHOD\s0
190implementations (eg. from an \s-1ENGINE\s0 module that supports embedded
191hardware-protected keys), and in such cases attempting to change the \s-1DH_METHOD\s0
192for the key can have unexpected results.
193.PP
194\&\fIDH_new_method()\fR allocates and initializes a \s-1DH\s0 structure so that \fBengine\fR will
195be used for the \s-1DH\s0 operations. If \fBengine\fR is \s-1NULL\s0, the default \s-1ENGINE\s0 for \s-1DH\s0
196operations is used, and if no default \s-1ENGINE\s0 is set, the \s-1DH_METHOD\s0 controlled by
197\&\fIDH_set_default_method()\fR is used.
198.SH "THE DH_METHOD STRUCTURE"
199.IX Header "THE DH_METHOD STRUCTURE"
200.Vb 4
201\& typedef struct dh_meth_st
202\& {
203\& /* name of the implementation */
204\& const char *name;
205.Ve
206.Vb 2
207\& /* generate private and public DH values for key agreement */
208\& int (*generate_key)(DH *dh);
209.Ve
210.Vb 2
211\& /* compute shared secret */
212\& int (*compute_key)(unsigned char *key, BIGNUM *pub_key, DH *dh);
213.Ve
214.Vb 4
215\& /* compute r = a ^ p mod m (May be NULL for some implementations) */
216\& int (*bn_mod_exp)(DH *dh, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
217\& const BIGNUM *m, BN_CTX *ctx,
218\& BN_MONT_CTX *m_ctx);
219.Ve
220.Vb 2
221\& /* called at DH_new */
222\& int (*init)(DH *dh);
223.Ve
224.Vb 2
225\& /* called at DH_free */
226\& int (*finish)(DH *dh);
227.Ve
228.Vb 1
229\& int flags;
230.Ve
231.Vb 1
232\& char *app_data; /* ?? */
233.Ve
234.Vb 1
235\& } DH_METHOD;
236.Ve
237.SH "RETURN VALUES"
238.IX Header "RETURN VALUES"
239\&\fIDH_OpenSSL()\fR and \fIDH_get_default_method()\fR return pointers to the respective
240\&\fB\s-1DH_METHOD\s0\fRs.
241.PP
242\&\fIDH_set_default_method()\fR returns no value.
243.PP
244\&\fIDH_set_method()\fR returns non-zero if the provided \fBmeth\fR was successfully set as
245the method for \fBdh\fR (including unloading the \s-1ENGINE\s0 handle if the previous
246method was supplied by an \s-1ENGINE\s0).
247.PP
248\&\fIDH_new_method()\fR returns \s-1NULL\s0 and sets an error code that can be obtained by
249ERR_get_error(3) if the allocation fails. Otherwise it
250returns a pointer to the newly allocated structure.
251.SH "NOTES"
252.IX Header "NOTES"
253As of version 0.9.7, \s-1DH_METHOD\s0 implementations are grouped together with other
254algorithmic APIs (eg. \s-1RSA_METHOD\s0, \s-1EVP_CIPHER\s0, etc) in \fB\s-1ENGINE\s0\fR modules. If a
255default \s-1ENGINE\s0 is specified for \s-1DH\s0 functionality using an \s-1ENGINE\s0 \s-1API\s0 function,
256that will override any \s-1DH\s0 defaults set using the \s-1DH\s0 \s-1API\s0 (ie.
257\&\fIDH_set_default_method()\fR). For this reason, the \s-1ENGINE\s0 \s-1API\s0 is the recommended way
258to control default implementations for use in \s-1DH\s0 and other cryptographic
259algorithms.
260.SH "SEE ALSO"
261.IX Header "SEE ALSO"
262dh(3), DH_new(3)
263.SH "HISTORY"
264.IX Header "HISTORY"
265\&\fIDH_set_default_method()\fR, \fIDH_get_default_method()\fR, \fIDH_set_method()\fR,
266\&\fIDH_new_method()\fR and \fIDH_OpenSSL()\fR were added in OpenSSL 0.9.4.
267.PP
268\&\fIDH_set_default_openssl_method()\fR and \fIDH_get_default_openssl_method()\fR replaced
269\&\fIDH_set_default_method()\fR and \fIDH_get_default_method()\fR respectively, and
270\&\fIDH_set_method()\fR and \fIDH_new_method()\fR were altered to use \fB\s-1ENGINE\s0\fRs rather than
271\&\fB\s-1DH_METHOD\s0\fRs during development of the engine version of OpenSSL 0.9.6. For
2720.9.7, the handling of defaults in the \s-1ENGINE\s0 \s-1API\s0 was restructured so that this
273change was reversed, and behaviour of the other functions resembled more closely
274the previous behaviour. The behaviour of defaults in the \s-1ENGINE\s0 \s-1API\s0 now
275transparently overrides the behaviour of defaults in the \s-1DH\s0 \s-1API\s0 without
276requiring changing these function prototypes.
| 142.UC
143.SH "NAME"
144DH_set_default_method, DH_get_default_method,
145DH_set_method, DH_new_method, DH_OpenSSL \- select \s-1DH\s0 method
146.SH "SYNOPSIS"
147.IX Header "SYNOPSIS"
148.Vb 2
149\& #include <openssl/dh.h>
150\& #include <openssl/engine.h>
151.Ve
152.Vb 1
153\& void DH_set_default_method(const DH_METHOD *meth);
154.Ve
155.Vb 1
156\& const DH_METHOD *DH_get_default_method(void);
157.Ve
158.Vb 1
159\& int DH_set_method(DH *dh, const DH_METHOD *meth);
160.Ve
161.Vb 1
162\& DH *DH_new_method(ENGINE *engine);
163.Ve
164.Vb 1
165\& const DH_METHOD *DH_OpenSSL(void);
166.Ve
167.SH "DESCRIPTION"
168.IX Header "DESCRIPTION"
169A \fB\s-1DH_METHOD\s0\fR specifies the functions that OpenSSL uses for Diffie-Hellman
170operations. By modifying the method, alternative implementations
171such as hardware accelerators may be used. \s-1IMPORTANT:\s0 See the \s-1NOTES\s0 section for
172important information about how these \s-1DH\s0 \s-1API\s0 functions are affected by the use
173of \fB\s-1ENGINE\s0\fR \s-1API\s0 calls.
174.PP
175Initially, the default \s-1DH_METHOD\s0 is the OpenSSL internal implementation, as
176returned by \fIDH_OpenSSL()\fR.
177.PP
178\&\fIDH_set_default_method()\fR makes \fBmeth\fR the default method for all \s-1DH\s0
179structures created later. \fB\s-1NB\s0\fR: This is true only whilst no \s-1ENGINE\s0 has been set
180as a default for \s-1DH\s0, so this function is no longer recommended.
181.PP
182\&\fIDH_get_default_method()\fR returns a pointer to the current default \s-1DH_METHOD\s0.
183However, the meaningfulness of this result is dependant on whether the \s-1ENGINE\s0
184\&\s-1API\s0 is being used, so this function is no longer recommended.
185.PP
186\&\fIDH_set_method()\fR selects \fBmeth\fR to perform all operations using the key \fBdh\fR.
187This will replace the \s-1DH_METHOD\s0 used by the \s-1DH\s0 key and if the previous method
188was supplied by an \s-1ENGINE\s0, the handle to that \s-1ENGINE\s0 will be released during the
189change. It is possible to have \s-1DH\s0 keys that only work with certain \s-1DH_METHOD\s0
190implementations (eg. from an \s-1ENGINE\s0 module that supports embedded
191hardware-protected keys), and in such cases attempting to change the \s-1DH_METHOD\s0
192for the key can have unexpected results.
193.PP
194\&\fIDH_new_method()\fR allocates and initializes a \s-1DH\s0 structure so that \fBengine\fR will
195be used for the \s-1DH\s0 operations. If \fBengine\fR is \s-1NULL\s0, the default \s-1ENGINE\s0 for \s-1DH\s0
196operations is used, and if no default \s-1ENGINE\s0 is set, the \s-1DH_METHOD\s0 controlled by
197\&\fIDH_set_default_method()\fR is used.
198.SH "THE DH_METHOD STRUCTURE"
199.IX Header "THE DH_METHOD STRUCTURE"
200.Vb 4
201\& typedef struct dh_meth_st
202\& {
203\& /* name of the implementation */
204\& const char *name;
205.Ve
206.Vb 2
207\& /* generate private and public DH values for key agreement */
208\& int (*generate_key)(DH *dh);
209.Ve
210.Vb 2
211\& /* compute shared secret */
212\& int (*compute_key)(unsigned char *key, BIGNUM *pub_key, DH *dh);
213.Ve
214.Vb 4
215\& /* compute r = a ^ p mod m (May be NULL for some implementations) */
216\& int (*bn_mod_exp)(DH *dh, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
217\& const BIGNUM *m, BN_CTX *ctx,
218\& BN_MONT_CTX *m_ctx);
219.Ve
220.Vb 2
221\& /* called at DH_new */
222\& int (*init)(DH *dh);
223.Ve
224.Vb 2
225\& /* called at DH_free */
226\& int (*finish)(DH *dh);
227.Ve
228.Vb 1
229\& int flags;
230.Ve
231.Vb 1
232\& char *app_data; /* ?? */
233.Ve
234.Vb 1
235\& } DH_METHOD;
236.Ve
237.SH "RETURN VALUES"
238.IX Header "RETURN VALUES"
239\&\fIDH_OpenSSL()\fR and \fIDH_get_default_method()\fR return pointers to the respective
240\&\fB\s-1DH_METHOD\s0\fRs.
241.PP
242\&\fIDH_set_default_method()\fR returns no value.
243.PP
244\&\fIDH_set_method()\fR returns non-zero if the provided \fBmeth\fR was successfully set as
245the method for \fBdh\fR (including unloading the \s-1ENGINE\s0 handle if the previous
246method was supplied by an \s-1ENGINE\s0).
247.PP
248\&\fIDH_new_method()\fR returns \s-1NULL\s0 and sets an error code that can be obtained by
249ERR_get_error(3) if the allocation fails. Otherwise it
250returns a pointer to the newly allocated structure.
251.SH "NOTES"
252.IX Header "NOTES"
253As of version 0.9.7, \s-1DH_METHOD\s0 implementations are grouped together with other
254algorithmic APIs (eg. \s-1RSA_METHOD\s0, \s-1EVP_CIPHER\s0, etc) in \fB\s-1ENGINE\s0\fR modules. If a
255default \s-1ENGINE\s0 is specified for \s-1DH\s0 functionality using an \s-1ENGINE\s0 \s-1API\s0 function,
256that will override any \s-1DH\s0 defaults set using the \s-1DH\s0 \s-1API\s0 (ie.
257\&\fIDH_set_default_method()\fR). For this reason, the \s-1ENGINE\s0 \s-1API\s0 is the recommended way
258to control default implementations for use in \s-1DH\s0 and other cryptographic
259algorithms.
260.SH "SEE ALSO"
261.IX Header "SEE ALSO"
262dh(3), DH_new(3)
263.SH "HISTORY"
264.IX Header "HISTORY"
265\&\fIDH_set_default_method()\fR, \fIDH_get_default_method()\fR, \fIDH_set_method()\fR,
266\&\fIDH_new_method()\fR and \fIDH_OpenSSL()\fR were added in OpenSSL 0.9.4.
267.PP
268\&\fIDH_set_default_openssl_method()\fR and \fIDH_get_default_openssl_method()\fR replaced
269\&\fIDH_set_default_method()\fR and \fIDH_get_default_method()\fR respectively, and
270\&\fIDH_set_method()\fR and \fIDH_new_method()\fR were altered to use \fB\s-1ENGINE\s0\fRs rather than
271\&\fB\s-1DH_METHOD\s0\fRs during development of the engine version of OpenSSL 0.9.6. For
2720.9.7, the handling of defaults in the \s-1ENGINE\s0 \s-1API\s0 was restructured so that this
273change was reversed, and behaviour of the other functions resembled more closely
274the previous behaviour. The behaviour of defaults in the \s-1ENGINE\s0 \s-1API\s0 now
275transparently overrides the behaviour of defaults in the \s-1DH\s0 \s-1API\s0 without
276requiring changing these function prototypes.
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