6 DH_generate_parameters_ex, DH_generate_parameters,
7 DH_check - generate and check Diffie-Hellman parameters
11 #include <openssl/dh.h>
13 int DH_generate_parameters_ex(DH *dh, int prime_len,int generator, BN_GENCB *cb);
15 int DH_check(DH *dh, int *codes);
19 DH *DH_generate_parameters(int prime_len, int generator,
20 void (*callback)(int, int, void *), void *cb_arg);
24 DH_generate_parameters_ex() generates Diffie-Hellman parameters that can
25 be shared among a group of users, and stores them in the provided B<DH>
26 structure. The pseudo-random number generator must be
27 seeded prior to calling DH_generate_parameters().
29 B<prime_len> is the length in bits of the safe prime to be generated.
30 B<generator> is a small number E<gt> 1, typically 2 or 5.
32 A callback function may be used to provide feedback about the progress
33 of the key generation. If B<cb> is not B<NULL>, it will be
34 called as described in L<BN_generate_prime(3)|BN_generate_prime(3)> while a random prime
35 number is generated, and when a prime has been found, B<BN_GENCB_call(cb, 3, 0)>
36 is called. See L<BN_generate_prime(3)|BN_generate_prime(3)> for information on
37 the BN_GENCB_call() function.
39 DH_check() validates Diffie-Hellman parameters. It checks that B<p> is
40 a safe prime, and that B<g> is a suitable generator. In the case of an
41 error, the bit flags DH_CHECK_P_NOT_SAFE_PRIME or
42 DH_NOT_SUITABLE_GENERATOR are set in B<*codes>.
43 DH_UNABLE_TO_CHECK_GENERATOR is set if the generator cannot be
44 checked, i.e. it does not equal 2 or 5.
48 DH_generate_parameters_ex() and DH_check() return 1 if the check could be
49 performed, 0 otherwise.
51 DH_generate_parameters() (deprecated) returns a pointer to the DH structure, or
52 NULL if the parameter generation fails.
54 The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
58 DH_generate_parameters_ex() and DH_generate_parameters() may run for several
59 hours before finding a suitable prime.
61 The parameters generated by DH_generate_parameters_ex() and DH_generate_parameters()
62 are not to be used in signature schemes.
66 If B<generator> is not 2 or 5, B<dh-E<gt>g>=B<generator> is not
71 L<dh(3)|dh(3)>, L<ERR_get_error(3)|ERR_get_error(3)>, L<rand(3)|rand(3)>,
72 L<DH_free(3)|DH_free(3)>
76 DH_check() is available in all versions of SSLeay and OpenSSL.
77 The B<cb_arg> argument to DH_generate_parameters() was added in SSLeay 0.9.0.
79 In versions before OpenSSL 0.9.5, DH_CHECK_P_NOT_STRONG_PRIME is used
80 instead of DH_CHECK_P_NOT_SAFE_PRIME.