1=pod 2 3=head1 NAME 4 5DH_generate_key, DH_compute_key - perform Diffie-Hellman key exchange 6 7=head1 SYNOPSIS 8 9 #include <openssl/dh.h> 10 11 int DH_generate_key(DH *dh); 12 13 int DH_compute_key(unsigned char *key, BIGNUM *pub_key, DH *dh); 14 15=head1 DESCRIPTION 16 17DH_generate_key() performs the first step of a Diffie-Hellman key 18exchange by generating private and public DH values. By calling 19DH_compute_key(), these are combined with the other party's public 20value to compute the shared key. 21 22DH_generate_key() expects B<dh> to contain the shared parameters 23B<dh-E<gt>p> and B<dh-E<gt>g>. It generates a random private DH value 24unless B<dh-E<gt>priv_key> is already set, and computes the 25corresponding public value B<dh-E<gt>pub_key>, which can then be 26published. 27 28DH_compute_key() computes the shared secret from the private DH value 29in B<dh> and the other party's public value in B<pub_key> and stores 30it in B<key>. B<key> must point to B<DH_size(dh)> bytes of memory. 31 32=head1 RETURN VALUES 33 34DH_generate_key() returns 1 on success, 0 otherwise. 35 36DH_compute_key() returns the size of the shared secret on success, -1 37on error. 38 39The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>. 40 41=head1 SEE ALSO 42 43L<dh(3)|dh(3)>, L<ERR_get_error(3)|ERR_get_error(3)>, L<rand(3)|rand(3)>, L<DH_size(3)|DH_size(3)> 44 45=head1 HISTORY 46 47DH_generate_key() and DH_compute_key() are available in all versions 48of SSLeay and OpenSSL. 49 50=cut 51