xref: /openssl/doc/man3/DH_set_method.pod (revision 3dbf8243)
1=pod
2
3=head1 NAME
4
5DH_set_default_method, DH_get_default_method,
6DH_set_method, DH_new_method, DH_OpenSSL - select DH method
7
8=head1 SYNOPSIS
9
10 #include <openssl/dh.h>
11
12The following functions have been deprecated since OpenSSL 3.0, and can be
13hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value,
14see L<openssl_user_macros(7)>:
15
16 void DH_set_default_method(const DH_METHOD *meth);
17
18 const DH_METHOD *DH_get_default_method(void);
19
20 int DH_set_method(DH *dh, const DH_METHOD *meth);
21
22 DH *DH_new_method(ENGINE *engine);
23
24 const DH_METHOD *DH_OpenSSL(void);
25
26=head1 DESCRIPTION
27
28All of the functions described on this page are deprecated.
29Applications should instead use the provider APIs.
30
31A B<DH_METHOD> specifies the functions that OpenSSL uses for Diffie-Hellman
32operations. By modifying the method, alternative implementations
33such as hardware accelerators may be used. IMPORTANT: See the NOTES section for
34important information about how these DH API functions are affected by the use
35of B<ENGINE> API calls.
36
37Initially, the default DH_METHOD is the OpenSSL internal implementation, as
38returned by DH_OpenSSL().
39
40DH_set_default_method() makes B<meth> the default method for all DH
41structures created later.
42B<NB>: This is true only whilst no ENGINE has been set
43as a default for DH, so this function is no longer recommended.
44This function is not thread-safe and should not be called at the same time
45as other OpenSSL functions.
46
47DH_get_default_method() returns a pointer to the current default DH_METHOD.
48However, the meaningfulness of this result is dependent on whether the ENGINE
49API is being used, so this function is no longer recommended.
50
51DH_set_method() selects B<meth> to perform all operations using the key B<dh>.
52This will replace the DH_METHOD used by the DH key and if the previous method
53was supplied by an ENGINE, the handle to that ENGINE will be released during the
54change. It is possible to have DH keys that only work with certain DH_METHOD
55implementations (e.g. from an ENGINE module that supports embedded
56hardware-protected keys), and in such cases attempting to change the DH_METHOD
57for the key can have unexpected results.
58
59DH_new_method() allocates and initializes a DH structure so that B<engine> will
60be used for the DH operations. If B<engine> is NULL, the default ENGINE for DH
61operations is used, and if no default ENGINE is set, the DH_METHOD controlled by
62DH_set_default_method() is used.
63
64A new DH_METHOD object may be constructed using DH_meth_new() (see
65L<DH_meth_new(3)>).
66
67=head1 RETURN VALUES
68
69DH_OpenSSL() and DH_get_default_method() return pointers to the respective
70B<DH_METHOD>s.
71
72DH_set_default_method() returns no value.
73
74DH_set_method() returns nonzero if the provided B<meth> was successfully set as
75the method for B<dh> (including unloading the ENGINE handle if the previous
76method was supplied by an ENGINE).
77
78DH_new_method() returns NULL and sets an error code that can be obtained by
79L<ERR_get_error(3)> if the allocation fails. Otherwise it
80returns a pointer to the newly allocated structure.
81
82=head1 SEE ALSO
83
84L<DH_new(3)>, L<DH_new(3)>, L<DH_meth_new(3)>
85
86=head1 HISTORY
87
88All of these functions were deprecated in OpenSSL 3.0.
89
90=head1 COPYRIGHT
91
92Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
93
94Licensed under the Apache License 2.0 (the "License").  You may not use
95this file except in compliance with the License.  You can obtain a copy
96in the file LICENSE in the source distribution or at
97L<https://www.openssl.org/source/license.html>.
98
99=cut
100