sub encrypt {
    my($proto, $target, $data) = @_;
    my $id = $target->email_address;
    my $key = $target->pgp_key;
    my $ring = Crypt::OpenPGP::KeyRing->new(Data => $key)
            or die "new KeyRing failed: $Crypt::OpenPGP::ErrorHandler::ERROR";
    my $pgp = Crypt::OpenPGP->new(PubRing => $ring)
            or die "new Context failed: $Crypt::OpenPGP::ErrorHandler::ERROR";
    $pgp->encrypt(
        Data => $data,
        Recipients => [ $id ],
        Armour => 1,
    );
}