1=pod
2
3=head1 NAME
4
5DH_generate_parameters_ex, DH_generate_parameters,
6DH_check, DH_check_params,
7DH_check_ex, DH_check_params_ex, DH_check_pub_key_ex
8- generate and check Diffie-Hellman
9parameters
10
11=head1 SYNOPSIS
12
13 #include <openssl/dh.h>
14
15The following functions have been deprecated since OpenSSL 3.0, and can be
16hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value,
17see L<openssl_user_macros(7)>:
18
19 int DH_generate_parameters_ex(DH *dh, int prime_len, int generator, BN_GENCB *cb);
20
21 int DH_check(DH *dh, int *codes);
22 int DH_check_params(DH *dh, int *codes);
23
24 int DH_check_ex(const DH *dh);
25 int DH_check_params_ex(const DH *dh);
26 int DH_check_pub_key_ex(const DH *dh, const BIGNUM *pub_key);
27
28The following functions have been deprecated since OpenSSL 0.9.8, and can be
29hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value,
30see L<openssl_user_macros(7)>:
31
32 DH *DH_generate_parameters(int prime_len, int generator,
33                            void (*callback)(int, int, void *), void *cb_arg);
34
35=head1 DESCRIPTION
36
37All of the functions described on this page are deprecated.
38Applications should instead use L<EVP_PKEY_check(3)>,
39L<EVP_PKEY_public_check(3)>, L<EVP_PKEY_private_check(3)> and
40L<EVP_PKEY_param_check(3)>.
41
42DH_generate_parameters_ex() generates Diffie-Hellman parameters that can
43be shared among a group of users, and stores them in the provided B<DH>
44structure. The pseudo-random number generator must be
45seeded before calling it.
46The parameters generated by DH_generate_parameters_ex() should not be used in
47signature schemes.
48
49B<prime_len> is the length in bits of the safe prime to be generated.
50B<generator> is a small number E<gt> 1, typically 2 or 5.
51
52A callback function may be used to provide feedback about the progress
53of the key generation. If B<cb> is not B<NULL>, it will be
54called as described in L<BN_generate_prime(3)> while a random prime
55number is generated, and when a prime has been found, B<BN_GENCB_call(cb, 3, 0)>
56is called. See L<BN_generate_prime_ex(3)> for information on
57the BN_GENCB_call() function.
58
59DH_generate_parameters() is similar to DH_generate_prime_ex() but
60expects an old-style callback function; see
61L<BN_generate_prime(3)> for information on the old-style callback.
62
63DH_check_params() confirms that the B<p> and B<g> are likely enough to
64be valid.
65This is a lightweight check, if a more thorough check is needed, use
66DH_check().
67The value of B<*codes> is updated with any problems found.
68If B<*codes> is zero then no problems were found, otherwise the
69following bits may be set:
70
71=over 4
72
73=item DH_CHECK_P_NOT_PRIME
74
75The parameter B<p> has been determined to not being an odd prime.
76Note that the lack of this bit doesn't guarantee that B<p> is a
77prime.
78
79=item DH_NOT_SUITABLE_GENERATOR
80
81The generator B<g> is not suitable.
82Note that the lack of this bit doesn't guarantee that B<g> is
83suitable, unless B<p> is known to be a strong prime.
84
85=item DH_MODULUS_TOO_SMALL
86
87The modulus is too small.
88
89=item DH_MODULUS_TOO_LARGE
90
91The modulus is too large.
92
93=back
94
95DH_check() confirms that the Diffie-Hellman parameters B<dh> are valid. The
96value of B<*codes> is updated with any problems found. If B<*codes> is zero then
97no problems were found, otherwise the following bits may be set:
98
99=over 4
100
101=item DH_CHECK_P_NOT_PRIME
102
103The parameter B<p> is not prime.
104
105=item DH_CHECK_P_NOT_SAFE_PRIME
106
107The parameter B<p> is not a safe prime and no B<q> value is present.
108
109=item DH_UNABLE_TO_CHECK_GENERATOR
110
111The generator B<g> cannot be checked for suitability.
112
113=item DH_NOT_SUITABLE_GENERATOR
114
115The generator B<g> is not suitable.
116
117=item DH_CHECK_Q_NOT_PRIME
118
119The parameter B<q> is not prime.
120
121=item DH_CHECK_INVALID_Q_VALUE
122
123The parameter B<q> is invalid.
124
125=item DH_CHECK_INVALID_J_VALUE
126
127The parameter B<j> is invalid.
128
129=back
130
131If 0 is returned or B<*codes> is set to a nonzero value the supplied
132parameters should not be used for Diffie-Hellman operations otherwise
133the security properties of the key exchange are not guaranteed.
134
135DH_check_ex(), DH_check_params() and DH_check_pub_key_ex() are similar to
136DH_check() and DH_check_params() respectively, but the error reasons are added
137to the thread's error queue instead of provided as return values from the
138function.
139
140=head1 RETURN VALUES
141
142DH_generate_parameters_ex(), DH_check() and DH_check_params() return 1
143if the check could be performed, 0 otherwise.
144
145DH_generate_parameters() returns a pointer to the DH structure or NULL if
146the parameter generation fails.
147
148DH_check_ex(), DH_check_params() and DH_check_pub_key_ex() return 1 if the
149check is successful, 0 for failed.
150
151The error codes can be obtained by L<ERR_get_error(3)>.
152
153=head1 SEE ALSO
154
155L<DH_new(3)>, L<ERR_get_error(3)>, L<RAND_bytes(3)>,
156L<DH_free(3)>
157
158=head1 HISTORY
159
160All of these functions were deprecated in OpenSSL 3.0.
161
162DH_generate_parameters() was deprecated in OpenSSL 0.9.8; use
163DH_generate_parameters_ex() instead.
164
165=head1 COPYRIGHT
166
167Copyright 2000-2023 The OpenSSL Project Authors. All Rights Reserved.
168
169Licensed under the Apache License 2.0 (the "License").  You may not use
170this file except in compliance with the License.  You can obtain a copy
171in the file LICENSE in the source distribution or at
172L<https://www.openssl.org/source/license.html>.
173
174=cut
175