1DH_METH_NEW(3)                      OpenSSL                     DH_METH_NEW(3)
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NAME

6       DH_meth_new, DH_meth_free, DH_meth_dup, DH_meth_get0_name,
7       DH_meth_set1_name, DH_meth_get_flags, DH_meth_set_flags,
8       DH_meth_get0_app_data, DH_meth_set0_app_data, DH_meth_get_generate_key,
9       DH_meth_set_generate_key, DH_meth_get_compute_key,
10       DH_meth_set_compute_key, DH_meth_get_bn_mod_exp,
11       DH_meth_set_bn_mod_exp, DH_meth_get_init, DH_meth_set_init,
12       DH_meth_get_finish, DH_meth_set_finish, DH_meth_get_generate_params,
13       DH_meth_set_generate_params - Routines to build up DH methods
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SYNOPSIS

16        #include <openssl/dh.h>
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18        DH_METHOD *DH_meth_new(const char *name, int flags);
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20        void DH_meth_free(DH_METHOD *dhm);
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22        DH_METHOD *DH_meth_dup(const DH_METHOD *dhm);
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24        const char *DH_meth_get0_name(const DH_METHOD *dhm);
25        int DH_meth_set1_name(DH_METHOD *dhm, const char *name);
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27        int DH_meth_get_flags(const DH_METHOD *dhm);
28        int DH_meth_set_flags(DH_METHOD *dhm, int flags);
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30        void *DH_meth_get0_app_data(const DH_METHOD *dhm);
31        int DH_meth_set0_app_data(DH_METHOD *dhm, void *app_data);
32
33        int (*DH_meth_get_generate_key(const DH_METHOD *dhm))(DH *);
34        int DH_meth_set_generate_key(DH_METHOD *dhm, int (*generate_key)(DH *));
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36        int (*DH_meth_get_compute_key(const DH_METHOD *dhm))
37            (unsigned char *key, const BIGNUM *pub_key, DH *dh);
38        int DH_meth_set_compute_key(DH_METHOD *dhm,
39            int (*compute_key)(unsigned char *key, const BIGNUM *pub_key, DH *dh));
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41        int (*DH_meth_get_bn_mod_exp(const DH_METHOD *dhm))
42            (const DH *dh, BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
43             const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
44        int DH_meth_set_bn_mod_exp(DH_METHOD *dhm,
45            int (*bn_mod_exp)(const DH *dh, BIGNUM *r, const BIGNUM *a,
46                              const BIGNUM *p, const BIGNUM *m, BN_CTX *ctx,
47                              BN_MONT_CTX *m_ctx));
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49        int (*DH_meth_get_init(const DH_METHOD *dhm))(DH *);
50        int DH_meth_set_init(DH_METHOD *dhm, int (*init)(DH *));
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52        int (*DH_meth_get_finish(const DH_METHOD *dhm))(DH *);
53        int DH_meth_set_finish(DH_METHOD *dhm, int (*finish)(DH *));
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55        int (*DH_meth_get_generate_params(const DH_METHOD *dhm))
56            (DH *, int, int, BN_GENCB *);
57        int DH_meth_set_generate_params(DH_METHOD *dhm,
58            int (*generate_params)(DH *, int, int, BN_GENCB *));
59

DESCRIPTION

61       The DH_METHOD type is a structure used for the provision of custom DH
62       implementations. It provides a set of functions used by OpenSSL for the
63       implementation of the various DH capabilities.
64
65       DH_meth_new() creates a new DH_METHOD structure. It should be given a
66       unique name and a set of flags. The name should be a NULL terminated
67       string, which will be duplicated and stored in the DH_METHOD object. It
68       is the callers responsibility to free the original string. The flags
69       will be used during the construction of a new DH object based on this
70       DH_METHOD. Any new DH object will have those flags set by default.
71
72       DH_meth_dup() creates a duplicate copy of the DH_METHOD object passed
73       as a parameter. This might be useful for creating a new DH_METHOD based
74       on an existing one, but with some differences.
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76       DH_meth_free() destroys a DH_METHOD structure and frees up any memory
77       associated with it.
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79       DH_meth_get0_name() will return a pointer to the name of this
80       DH_METHOD. This is a pointer to the internal name string and so should
81       not be freed by the caller. DH_meth_set1_name() sets the name of the
82       DH_METHOD to name. The string is duplicated and the copy is stored in
83       the DH_METHOD structure, so the caller remains responsible for freeing
84       the memory associated with the name.
85
86       DH_meth_get_flags() returns the current value of the flags associated
87       with this DH_METHOD. DH_meth_set_flags() provides the ability to set
88       these flags.
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90       The functions DH_meth_get0_app_data() and DH_meth_set0_app_data()
91       provide the ability to associate implementation specific data with the
92       DH_METHOD. It is the application's responsibility to free this data
93       before the DH_METHOD is freed via a call to DH_meth_free().
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95       DH_meth_get_generate_key() and DH_meth_set_generate_key() get and set
96       the function used for generating a new DH key pair respectively. This
97       function will be called in response to the application calling
98       DH_generate_key(). The parameter for the function has the same meaning
99       as for DH_generate_key().
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101       DH_meth_get_compute_key() and DH_meth_set_compute_key() get and set the
102       function used for computing a new DH shared secret respectively. This
103       function will be called in response to the application calling
104       DH_compute_key(). The parameters for the function have the same meaning
105       as for DH_compute_key().
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107       DH_meth_get_bn_mod_exp() and DH_meth_set_bn_mod_exp() get and set the
108       function used for computing the following value:
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110        r = a ^ p mod m
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112       This function will be called by the default OpenSSL function for
113       DH_generate_key(). The result is stored in the r parameter. This
114       function may be NULL unless using the default generate key function, in
115       which case it must be present.
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117       DH_meth_get_init() and DH_meth_set_init() get and set the function used
118       for creating a new DH instance respectively. This function will be
119       called in response to the application calling DH_new() (if the current
120       default DH_METHOD is this one) or DH_new_method(). The DH_new() and
121       DH_new_method() functions will allocate the memory for the new DH
122       object, and a pointer to this newly allocated structure will be passed
123       as a parameter to the function. This function may be NULL.
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125       DH_meth_get_finish() and DH_meth_set_finish() get and set the function
126       used for destroying an instance of a DH object respectively. This
127       function will be called in response to the application calling
128       DH_free(). A pointer to the DH to be destroyed is passed as a
129       parameter. The destroy function should be used for DH implementation
130       specific clean up. The memory for the DH itself should not be freed by
131       this function. This function may be NULL.
132
133       DH_meth_get_generate_params() and DH_meth_set_generate_params() get and
134       set the function used for generating DH parameters respectively. This
135       function will be called in response to the application calling
136       DH_generate_parameters_ex() (or DH_generate_parameters()). The
137       parameters for the function have the same meaning as for
138       DH_generate_parameters_ex(). This function may be NULL.
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RETURN VALUES

141       DH_meth_new() and DH_meth_dup() return the newly allocated DH_METHOD
142       object or NULL on failure.
143
144       DH_meth_get0_name() and DH_meth_get_flags() return the name and flags
145       associated with the DH_METHOD respectively.
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147       All other DH_meth_get_*() functions return the appropriate function
148       pointer that has been set in the DH_METHOD, or NULL if no such pointer
149       has yet been set.
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151       DH_meth_set1_name() and all DH_meth_set_*() functions return 1 on
152       success or 0 on failure.
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SEE ALSO

155       DH_new(3), DH_new(3), DH_generate_parameters(3), DH_generate_key(3),
156       DH_set_method(3), DH_size(3), DH_get0_pqg(3)
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HISTORY

159       The functions described here were added in OpenSSL 1.1.0.
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162       Copyright 2016-2018 The OpenSSL Project Authors. All Rights Reserved.
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164       Licensed under the OpenSSL license (the "License").  You may not use
165       this file except in compliance with the License.  You can obtain a copy
166       in the file LICENSE in the source distribution or at
167       <https://www.openssl.org/source/license.html>.
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1711.1.1i                            2021-07-22                    DH_METH_NEW(3)
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