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authorbeck <>2000-03-19 11:13:58 +0000
committerbeck <>2000-03-19 11:13:58 +0000
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OpenSSL 0.9.5 merge
*warning* this bumps shared lib minors for libssl and libcrypto from 2.1 to 2.2 if you are using the ssl26 packages for ssh and other things to work you will need to get new ones (see ~beck/libsslsnap/<arch>) on cvs or ~beck/src-patent.tar.gz on cvs
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1=pod
2
3=head1 NAME
4
5DH_generate_parameters, DH_check - generate and check Diffie-Hellman parameters
6
7=head1 SYNOPSIS
8
9 #include <openssl/dh.h>
10
11 DH *DH_generate_parameters(int prime_len, int generator,
12 void (*callback)(int, int, void *), void *cb_arg);
13
14 int DH_check(DH *dh, int *codes);
15
16=head1 DESCRIPTION
17
18DH_generate_parameters() generates Diffie-Hellman parameters that can
19be shared among a group of users, and returns them in a newly
20allocated B<DH> structure. The pseudo-random number generator must be
21seeded prior to calling DH_generate_parameters().
22
23B<prime_len> is the length in bits of the safe prime to be generated.
24B<generator> is a small number E<gt> 1, typically 2 or 5.
25
26A callback function may be used to provide feedback about the progress
27of the key generation. If B<callback> is not B<NULL>, it will be
28called as described in L<BN_generate_prime(3)|BN_generate_prime(3)> while a random prime
29number is generated, and when a prime has been found, B<callback(3,
300, cb_arg)> is called.
31
32DH_check() validates Diffie-Hellman parameters. It checks that B<p> is
33a safe prime, and that B<g> is a suitable generator. In the case of an
34error, the bit flags DH_CHECK_P_NOT_SAFE_PRIME or
35DH_NOT_SUITABLE_GENERATOR are set in B<*codes>.
36DH_UNABLE_TO_CHECK_GENERATOR is set if the generator cannot be
37checked, i.e. it does not equal 2 or 5.
38
39=head1 RETURN VALUES
40
41DH_generate_parameters() returns a pointer to the DH structure, or
42NULL if the parameter generation fails. The error codes can be
43obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
44
45DH_check() returns 1 if the check could be performed, 0 otherwise.
46
47=head1 NOTES
48
49DH_generate_parameters() may run for several hours before finding a
50suitable prime.
51
52The parameters generated by DH_generate_parameters() are not to be
53used in signature schemes.
54
55=head1 BUGS
56
57If B<generator> is not 2 or 5, B<dh-E<gt>g>=B<generator> is not
58a usable generator.
59
60=head1 SEE ALSO
61
62L<dh(3)|dh(3)>, L<err(3)|err(3)>, L<rand(3)|rand(3)>, L<DH_free(3)|DH_free(3)>
63
64=head1 HISTORY
65
66DH_check() is available in all versions of SSLeay and OpenSSL.
67The B<cb_arg> argument to DH_generate_parameters() was added in SSLeay 0.9.0.
68
69In versions before OpenSSL 0.9.5, DH_CHECK_P_NOT_STRONG_PRIME is used
70instead of DH_CHECK_P_NOT_SAFE_PRIME.
71
72=cut