.rn '' }`
'''
'''
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..
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'''
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..
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.TH DH_set_method 3 "0.9.5a" "22/Jul/100" "OpenSSL"
.UC
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.rm #[ #] #H #V #F C
.SH "NAME"
DH_set_default_method, DH_get_default_method, DH_set_method,
DH_new_method, DH_OpenSSL \- select DH method
.SH "LIBRARY"
libcrypto, -lcrypto
.SH "SYNOPSIS"
.PP
.Vb 1
\& #include <openssl/dh.h>
.Ve
.Vb 1
\& void DH_set_default_method(DH_METHOD *meth);
.Ve
.Vb 1
\& DH_METHOD *DH_get_default_method(void);
.Ve
.Vb 1
\& DH_METHOD *DH_set_method(DH *dh, DH_METHOD *meth);
.Ve
.Vb 1
\& DH *DH_new_method(DH_METHOD *meth);
.Ve
.Vb 1
\& DH_METHOD *DH_OpenSSL(void);
.Ve
.SH "DESCRIPTION"
A \fBDH_METHOD\fR specifies the functions that OpenSSL uses for Diffie-Hellman
operations. By modifying the method, alternative implementations
such as hardware accelerators may be used.
.PP
Initially, the default is to use the OpenSSL internal implementation.
\fIDH_OpenSSL()\fR returns a pointer to that method.
.PP
\fIDH_set_default_method()\fR makes \fBmeth\fR the default method for all \fBDH\fR
structures created later.
.PP
\fIDH_get_default_method()\fR returns a pointer to the current default
method.
.PP
\fIDH_set_method()\fR selects \fBmeth\fR for all operations using the structure \fBdh\fR.
.PP
\fIDH_get_method()\fR returns a pointer to the method currently selected
for \fBdh\fR.
.PP
\fIDH_new_method()\fR allocates and initializes a \fBDH\fR structure so that
\fBmethod\fR will be used for the DH operations. If \fBmethod\fR is \fBNULL\fR,
the default method is used.
.SH "THE DH_METHOD STRUCTURE"
.PP
.Vb 4
\& typedef struct dh_meth_st
\& {
\&     /* name of the implementation */
\&        const char *name;
.Ve
.Vb 2
\&     /* generate private and public DH values for key agreement */
\&        int (*generate_key)(DH *dh);
.Ve
.Vb 2
\&     /* compute shared secret */
\&        int (*compute_key)(unsigned char *key, BIGNUM *pub_key, DH *dh);
.Ve
.Vb 4
\&     /* compute r = a ^ p mod m (May be NULL for some implementations) */
\&        int (*bn_mod_exp)(DH *dh, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
\&                                const BIGNUM *m, BN_CTX *ctx,
\&                                BN_MONT_CTX *m_ctx);
.Ve
.Vb 2
\&     /* called at DH_new */
\&        int (*init)(DH *dh);
.Ve
.Vb 2
\&     /* called at DH_free */
\&        int (*finish)(DH *dh);
.Ve
.Vb 1
\&        int flags;
.Ve
.Vb 1
\&        char *app_data; /* ?? */
.Ve
.Vb 1
\& } DH_METHOD;
.Ve
.SH "RETURN VALUES"
\fIDH_OpenSSL()\fR, \fIDH_get_default_method()\fR and \fIDH_get_method()\fR return
pointers to the respective \fBDH_METHOD\fRs.
.PP
\fIDH_set_default_method()\fR returns no value.
.PP
\fIDH_set_method()\fR returns a pointer to the \fBDH_METHOD\fR previously
associated with \fBdh\fR.
.PP
\fIDH_new_method()\fR returns \fBNULL\fR and sets an error code that can be
obtained by the \fIERR_get_error(3)|ERR_get_error(3)\fR manpage if the allocation fails. Otherwise it
returns a pointer to the newly allocated structure.
.SH "SEE ALSO"
the \fIdh(3)|dh(3)\fR manpage, the \fIDH_new(3)|DH_new(3)\fR manpage
.SH "HISTORY"
\fIDH_set_default_method()\fR, \fIDH_get_default_method()\fR, \fIDH_set_method()\fR,
\fIDH_new_method()\fR and \fIDH_OpenSSL()\fR were added in OpenSSL 0.9.4.

.rn }` ''
.IX Title "DH_set_method 3"
.IX Name "DH_set_default_method, DH_get_default_method, DH_set_method,
DH_new_method, DH_OpenSSL - select DH method"

.IX Header "NAME"

.IX Header "SYNOPSIS"

.IX Header "DESCRIPTION"

.IX Header "THE DH_METHOD STRUCTURE"

.IX Header "RETURN VALUES"

.IX Header "SEE ALSO"

.IX Header "HISTORY"