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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" DH_meth_new, DH_meth_free, DH_meth_dup, DH_meth_get0_name, DH_meth_set1_name, DH_meth_get_flags, DH_meth_set_flags, DH_meth_get0_app_data, DH_meth_set0_app_data, DH_meth_get_generate_key, DH_meth_set_generate_key, DH_meth_get_compute_key, DH_meth_set_compute_key, DH_meth_get_bn_mod_exp, DH_meth_set_bn_mod_exp, DH_meth_get_init, DH_meth_set_init, DH_meth_get_finish, DH_meth_set_finish, DH_meth_get_generate_params, DH_meth_set_generate_params \- Routines to build up DH methods .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #include <openssl/dh.h> \& \& DH_METHOD *DH_meth_new(const char *name, int flags); \& \& void DH_meth_free(DH_METHOD *dhm); \& \& DH_METHOD *DH_meth_dup(const DH_METHOD *dhm); \& \& const char *DH_meth_get0_name(const DH_METHOD *dhm); \& int DH_meth_set1_name(DH_METHOD *dhm, const char *name); \& \& int DH_meth_get_flags(const DH_METHOD *dhm); \& int DH_meth_set_flags(DH_METHOD *dhm, int flags); \& \& void *DH_meth_get0_app_data(const DH_METHOD *dhm); \& int DH_meth_set0_app_data(DH_METHOD *dhm, void *app_data); \& \& int (*DH_meth_get_generate_key(const DH_METHOD *dhm))(DH *); \& int DH_meth_set_generate_key(DH_METHOD *dhm, int (*generate_key)(DH *)); \& \& int (*DH_meth_get_compute_key(const DH_METHOD *dhm)) \& (unsigned char *key, const BIGNUM *pub_key, DH *dh); \& int DH_meth_set_compute_key(DH_METHOD *dhm, \& int (*compute_key)(unsigned char *key, const BIGNUM *pub_key, DH *dh)); \& \& int (*DH_meth_get_bn_mod_exp(const DH_METHOD *dhm)) \& (const DH *dh, BIGNUM *r, const BIGNUM *a, const BIGNUM *p, \& const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx); \& int DH_meth_set_bn_mod_exp(DH_METHOD *dhm, \& int (*bn_mod_exp)(const DH *dh, BIGNUM *r, const BIGNUM *a, \& const BIGNUM *p, const BIGNUM *m, BN_CTX *ctx, \& BN_MONT_CTX *m_ctx)); \& \& int (*DH_meth_get_init(const DH_METHOD *dhm))(DH *); \& int DH_meth_set_init(DH_METHOD *dhm, int (*init)(DH *)); \& \& int (*DH_meth_get_finish(const DH_METHOD *dhm))(DH *); \& int DH_meth_set_finish(DH_METHOD *dhm, int (*finish)(DH *)); \& \& int (*DH_meth_get_generate_params(const DH_METHOD *dhm)) \& (DH *, int, int, BN_GENCB *); \& int DH_meth_set_generate_params(DH_METHOD *dhm, \& int (*generate_params)(DH *, int, int, BN_GENCB *)); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" The \fB\s-1DH_METHOD\s0\fR type is a structure used for the provision of custom \s-1DH\s0 implementations. It provides a set of functions used by OpenSSL for the implementation of the various \s-1DH\s0 capabilities. .PP \&\fBDH_meth_new()\fR creates a new \fB\s-1DH_METHOD\s0\fR structure. It should be given a unique \fBname\fR and a set of \fBflags\fR. The \fBname\fR should be a \s-1NULL\s0 terminated string, which will be duplicated and stored in the \fB\s-1DH_METHOD\s0\fR object. It is the callers responsibility to free the original string. The flags will be used during the construction of a new \fB\s-1DH\s0\fR object based on this \fB\s-1DH_METHOD\s0\fR. Any new \fB\s-1DH\s0\fR object will have those flags set by default. .PP \&\fBDH_meth_dup()\fR creates a duplicate copy of the \fB\s-1DH_METHOD\s0\fR object passed as a parameter. This might be useful for creating a new \fB\s-1DH_METHOD\s0\fR based on an existing one, but with some differences. .PP \&\fBDH_meth_free()\fR destroys a \fB\s-1DH_METHOD\s0\fR structure and frees up any memory associated with it. .PP \&\fBDH_meth_get0_name()\fR will return a pointer to the name of this \s-1DH_METHOD.\s0 This is a pointer to the internal name string and so should not be freed by the caller. \fBDH_meth_set1_name()\fR sets the name of the \s-1DH_METHOD\s0 to \fBname\fR. The string is duplicated and the copy is stored in the \s-1DH_METHOD\s0 structure, so the caller remains responsible for freeing the memory associated with the name. .PP \&\fBDH_meth_get_flags()\fR returns the current value of the flags associated with this \&\s-1DH_METHOD.\s0 \fBDH_meth_set_flags()\fR provides the ability to set these flags. .PP The functions \fBDH_meth_get0_app_data()\fR and \fBDH_meth_set0_app_data()\fR provide the ability to associate implementation specific data with the \s-1DH_METHOD.\s0 It is the application's responsibility to free this data before the \s-1DH_METHOD\s0 is freed via a call to \fBDH_meth_free()\fR. .PP \&\fBDH_meth_get_generate_key()\fR and \fBDH_meth_set_generate_key()\fR get and set the function used for generating a new \s-1DH\s0 key pair respectively. This function will be called in response to the application calling \fBDH_generate_key()\fR. The parameter for the function has the same meaning as for \fBDH_generate_key()\fR. .PP \&\fBDH_meth_get_compute_key()\fR and \fBDH_meth_set_compute_key()\fR get and set the function used for computing a new \s-1DH\s0 shared secret respectively. This function will be called in response to the application calling \fBDH_compute_key()\fR. The parameters for the function have the same meaning as for \fBDH_compute_key()\fR. .PP \&\fBDH_meth_get_bn_mod_exp()\fR and \fBDH_meth_set_bn_mod_exp()\fR get and set the function used for computing the following value: .PP .Vb 1 \& r = a ^ p mod m .Ve .PP This function will be called by the default OpenSSL function for \&\fBDH_generate_key()\fR. The result is stored in the \fBr\fR parameter. This function may be \s-1NULL\s0 unless using the default generate key function, in which case it must be present. .PP \&\fBDH_meth_get_init()\fR and \fBDH_meth_set_init()\fR get and set the function used for creating a new \s-1DH\s0 instance respectively. This function will be called in response to the application calling \fBDH_new()\fR (if the current default \&\s-1DH_METHOD\s0 is this one) or \fBDH_new_method()\fR. The \fBDH_new()\fR and \fBDH_new_method()\fR functions will allocate the memory for the new \s-1DH\s0 object, and a pointer to this newly allocated structure will be passed as a parameter to the function. This function may be \s-1NULL.\s0 .PP \&\fBDH_meth_get_finish()\fR and \fBDH_meth_set_finish()\fR get and set the function used for destroying an instance of a \s-1DH\s0 object respectively. This function will be called in response to the application calling \fBDH_free()\fR. A pointer to the \s-1DH\s0 to be destroyed is passed as a parameter. The destroy function should be used for \s-1DH\s0 implementation specific clean up. The memory for the \s-1DH\s0 itself should not be freed by this function. This function may be \s-1NULL.\s0 .PP \&\fBDH_meth_get_generate_params()\fR and \fBDH_meth_set_generate_params()\fR get and set the function used for generating \s-1DH\s0 parameters respectively. This function will be called in response to the application calling \fBDH_generate_parameters_ex()\fR (or \&\fBDH_generate_parameters()\fR). The parameters for the function have the same meaning as for \fBDH_generate_parameters_ex()\fR. This function may be \s-1NULL.\s0 .SH "RETURN VALUES" .IX Header "RETURN VALUES" \&\fBDH_meth_new()\fR and \fBDH_meth_dup()\fR return the newly allocated \s-1DH_METHOD\s0 object or \s-1NULL\s0 on failure. .PP \&\fBDH_meth_get0_name()\fR and \fBDH_meth_get_flags()\fR return the name and flags associated with the \s-1DH_METHOD\s0 respectively. .PP All other DH_meth_get_*() functions return the appropriate function pointer that has been set in the \s-1DH_METHOD,\s0 or \s-1NULL\s0 if no such pointer has yet been set. .PP \&\fBDH_meth_set1_name()\fR and all DH_meth_set_*() functions return 1 on success or 0 on failure. .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBDH_new\fR\|(3), \fBDH_new\fR\|(3), \fBDH_generate_parameters\fR\|(3), \fBDH_generate_key\fR\|(3), \&\fBDH_set_method\fR\|(3), \fBDH_size\fR\|(3), \fBDH_get0_pqg\fR\|(3) .SH "HISTORY" .IX Header "HISTORY" The functions described here were added in OpenSSL 1.1.0. .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2016\-2018 The OpenSSL Project Authors. All Rights Reserved. .PP Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.