1 .\" Automatically generated by Pod::Man v1.37, Pod::Parser v1.35
4 .\" ========================================================================
5 .de Sh \" Subsection heading
13 .de Sp \" Vertical space (when we can't use .PP)
17 .de Vb \" Begin verbatim text
22 .de Ve \" End verbatim text
26 .\" Set up some character translations and predefined strings. \*(-- will
27 .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
28 .\" double quote, and \*(R" will give a right double quote. | will give a
29 .\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used to
30 .\" do unbreakable dashes and therefore won't be available. \*(C` and \*(C'
31 .\" expand to `' in nroff, nothing in troff, for use with C<>.
33 .ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
37 . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
38 . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch
51 .\" If the F register is turned on, we'll generate index entries on stderr for
52 .\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index
53 .\" entries marked with X<> in POD. Of course, you'll have to process the
54 .\" output yourself in some meaningful fashion.
57 . tm Index:\\$1\t\\n%\t"\\$2"
63 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
64 .\" way too many mistakes in technical documents.
68 .\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
69 .\" Fear. Run. Save yourself. No user-serviceable parts.
70 . \" fudge factors for nroff and troff
79 . ds #H ((1u-(\\\\n(.fu%2u))*.13m)
85 . \" simple accents for nroff and troff
95 . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
96 . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
97 . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
98 . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
99 . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
100 . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
102 . \" troff and (daisy-wheel) nroff accents
103 .ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
104 .ds 8 \h'\*(#H'\(*b\h'-\*(#H'
105 .ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
106 .ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
107 .ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
108 .ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
109 .ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
110 .ds ae a\h'-(\w'a'u*4/10)'e
111 .ds Ae A\h'-(\w'A'u*4/10)'E
112 . \" corrections for vroff
113 .if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
114 .if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
115 . \" for low resolution devices (crt and lpr)
116 .if \n(.H>23 .if \n(.V>19 \
129 .\" ========================================================================
131 .IX Title "DH_set_method 3"
132 .TH DH_set_method 3 "2007-03-15" "0.9.8e" "OpenSSL"
134 DH_set_default_method, DH_get_default_method,
135 DH_set_method, DH_new_method, DH_OpenSSL \- select DH method
137 .IX Header "SYNOPSIS"
139 \& #include <openssl/dh.h>
140 \& #include <openssl/engine.h>
144 \& void DH_set_default_method(const DH_METHOD *meth);
148 \& const DH_METHOD *DH_get_default_method(void);
152 \& int DH_set_method(DH *dh, const DH_METHOD *meth);
156 \& DH *DH_new_method(ENGINE *engine);
160 \& const DH_METHOD *DH_OpenSSL(void);
163 .IX Header "DESCRIPTION"
164 A \fB\s-1DH_METHOD\s0\fR specifies the functions that OpenSSL uses for Diffie-Hellman
165 operations. By modifying the method, alternative implementations
166 such as hardware accelerators may be used. \s-1IMPORTANT:\s0 See the \s-1NOTES\s0 section for
167 important information about how these \s-1DH\s0 \s-1API\s0 functions are affected by the use
168 of \fB\s-1ENGINE\s0\fR \s-1API\s0 calls.
170 Initially, the default \s-1DH_METHOD\s0 is the OpenSSL internal implementation, as
171 returned by \fIDH_OpenSSL()\fR.
173 \&\fIDH_set_default_method()\fR makes \fBmeth\fR the default method for all \s-1DH\s0
174 structures created later. \fB\s-1NB\s0\fR: This is true only whilst no \s-1ENGINE\s0 has been set
175 as a default for \s-1DH\s0, so this function is no longer recommended.
177 \&\fIDH_get_default_method()\fR returns a pointer to the current default \s-1DH_METHOD\s0.
178 However, 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.
181 \&\fIDH_set_method()\fR selects \fBmeth\fR to perform all operations using the key \fBdh\fR.
182 This will replace the \s-1DH_METHOD\s0 used by the \s-1DH\s0 key and if the previous method
183 was supplied by an \s-1ENGINE\s0, the handle to that \s-1ENGINE\s0 will be released during the
184 change. It is possible to have \s-1DH\s0 keys that only work with certain \s-1DH_METHOD\s0
185 implementations (eg. from an \s-1ENGINE\s0 module that supports embedded
186 hardware-protected keys), and in such cases attempting to change the \s-1DH_METHOD\s0
187 for the key can have unexpected results.
189 \&\fIDH_new_method()\fR allocates and initializes a \s-1DH\s0 structure so that \fBengine\fR will
190 be used for the \s-1DH\s0 operations. If \fBengine\fR is \s-1NULL\s0, the default \s-1ENGINE\s0 for \s-1DH\s0
191 operations 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.
193 .SH "THE DH_METHOD STRUCTURE"
194 .IX Header "THE DH_METHOD STRUCTURE"
196 \& typedef struct dh_meth_st
198 \& /* name of the implementation */
203 \& /* generate private and public DH values for key agreement */
204 \& int (*generate_key)(DH *dh);
208 \& /* compute shared secret */
209 \& int (*compute_key)(unsigned char *key, BIGNUM *pub_key, DH *dh);
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);
220 \& /* called at DH_new */
221 \& int (*init)(DH *dh);
225 \& /* called at DH_free */
226 \& int (*finish)(DH *dh);
234 \& char *app_data; /* ?? */
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.
245 \&\fIDH_set_default_method()\fR returns no value.
247 \&\fIDH_set_method()\fR returns non-zero if the provided \fBmeth\fR was successfully set as
248 the method for \fBdh\fR (including unloading the \s-1ENGINE\s0 handle if the previous
249 method was supplied by an \s-1ENGINE\s0).
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
253 returns a pointer to the newly allocated structure.
256 As of version 0.9.7, \s-1DH_METHOD\s0 implementations are grouped together with other
257 algorithmic APIs (eg. \s-1RSA_METHOD\s0, \s-1EVP_CIPHER\s0, etc) in \fB\s-1ENGINE\s0\fR modules. If a
258 default \s-1ENGINE\s0 is specified for \s-1DH\s0 functionality using an \s-1ENGINE\s0 \s-1API\s0 function,
259 that 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
261 to control default implementations for use in \s-1DH\s0 and other cryptographic
264 .IX Header "SEE ALSO"
265 \&\fIdh\fR\|(3), \fIDH_new\fR\|(3)
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.
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
275 0.9.7, the handling of defaults in the \s-1ENGINE\s0 \s-1API\s0 was restructured so that this
276 change was reversed, and behaviour of the other functions resembled more closely
277 the previous behaviour. The behaviour of defaults in the \s-1ENGINE\s0 \s-1API\s0 now
278 transparently overrides the behaviour of defaults in the \s-1DH\s0 \s-1API\s0 without
279 requiring changing these function prototypes.