#!/usr/bin/perl -w
    use strict;

    use Getopt::Std;
    getopts("d", \my %opts);
    my $d = $opts{d} || 0;

    use Crypt::RSA;

    my($key, $n) = (shift, shift);
    die "usage: $0 [-d] <k> <n>" unless $key && $n;

    my $rsa = Crypt::RSA->new($key, $n);
    my $c = do { local $/; <STDIN> };

    if ($opts{d}) {
        print $rsa->decrypt($c);
    }
    else {
        print $rsa->encrypt($c);
    }