1=pod 2 3=head1 NAME 4 5 6DH_generate_parameters_ex, DH_generate_parameters, 7DH_check - generate and check Diffie-Hellman parameters 8 9=head1 SYNOPSIS 10 11 #include <openssl/dh.h> 12 13 int DH_generate_parameters_ex(DH *dh, int prime_len,int generator, BN_GENCB *cb); 14 15 int DH_check(DH *dh, int *codes); 16 17Deprecated: 18 19 DH *DH_generate_parameters(int prime_len, int generator, 20 void (*callback)(int, int, void *), void *cb_arg); 21 22=head1 DESCRIPTION 23 24DH_generate_parameters_ex() generates Diffie-Hellman parameters that can 25be shared among a group of users, and stores them in the provided B<DH> 26structure. The pseudo-random number generator must be 27seeded prior to calling DH_generate_parameters(). 28 29B<prime_len> is the length in bits of the safe prime to be generated. 30B<generator> is a small number E<gt> 1, typically 2 or 5. 31 32A callback function may be used to provide feedback about the progress 33of the key generation. If B<cb> is not B<NULL>, it will be 34called as described in L<BN_generate_prime(3)|BN_generate_prime(3)> while a random prime 35number is generated, and when a prime has been found, B<BN_GENCB_call(cb, 3, 0)> 36is called. See L<BN_generate_prime(3)|BN_generate_prime(3)> for information on 37the BN_GENCB_call() function. 38 39DH_check() validates Diffie-Hellman parameters. It checks that B<p> is 40a safe prime, and that B<g> is a suitable generator. In the case of an 41error, the bit flags DH_CHECK_P_NOT_SAFE_PRIME or 42DH_NOT_SUITABLE_GENERATOR are set in B<*codes>. 43DH_UNABLE_TO_CHECK_GENERATOR is set if the generator cannot be 44checked, i.e. it does not equal 2 or 5. 45 46=head1 RETURN VALUES 47 48DH_generate_parameters_ex() and DH_check() return 1 if the check could be 49performed, 0 otherwise. 50 51DH_generate_parameters() (deprecated) returns a pointer to the DH structure, or 52NULL if the parameter generation fails. 53 54The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>. 55 56=head1 NOTES 57 58DH_generate_parameters_ex() and DH_generate_parameters() may run for several 59hours before finding a suitable prime. 60 61The parameters generated by DH_generate_parameters_ex() and DH_generate_parameters() 62are not to be used in signature schemes. 63 64=head1 BUGS 65 66If B<generator> is not 2 or 5, B<dh-E<gt>g>=B<generator> is not 67a usable generator. 68 69=head1 SEE ALSO 70 71L<dh(3)|dh(3)>, L<ERR_get_error(3)|ERR_get_error(3)>, L<rand(3)|rand(3)>, 72L<DH_free(3)|DH_free(3)> 73 74=head1 HISTORY 75 76DH_check() is available in all versions of SSLeay and OpenSSL. 77The B<cb_arg> argument to DH_generate_parameters() was added in SSLeay 0.9.0. 78 79In versions before OpenSSL 0.9.5, DH_CHECK_P_NOT_STRONG_PRIME is used 80instead of DH_CHECK_P_NOT_SAFE_PRIME. 81 82=cut 83