use Crypt::PBC;

my $pairing = new Crypt::PBC("params_d.txt");
my $P       = $pairing->init_G2->random; # generator in G2
my $s       = $pairing->init_Zr->random; # master secret
my $P_pub   = $pairing->init_G2->pow_zn($P, $s); # master public key