xor-base64.pl - encrypt/decrypt a string with XOR and base64

Posted by Stefan Schurtz on Sunday, December 25. 2011

Here is a little tool written in perl, which XOR a string against a key and outputs the result base64 encoded and vice versa.

Encrypt

./xor-base64.pl -e foobar -k deadbeef
[+] Cleartext: foobar
[+] Key: deadbeef
[+] Hex: 020a0e060317
[+] Ciphertext: AgoOBgMX

Decrypt

./xor-base64.pl -d AgoOBgMX -k deadbeef
[+] Ciphertext: AgoOBgMX
[+] Hex: 020a0e060317
[+] Key: deadbeef
[+] Cleartext: foobar

And here is the code

#!/usr/bin/perl

            use MIME::Base64;

            use Getopt::Long;

            use strict;

            ######################################

            # variables

            ######################################

            my $cstring;

            my $cipher;

            my @carray;

            my @key;

            ######################################

            # process commandline argmuments

            ######################################

            my ($help,$encrypt,$decrypt,$ikey);

            USAGE() if (@ARGV < 1 or ! GetOptions(

                            'help|h' => $help,

                            'version|v' => &VERSION,

                            'decrypt|d=s' => $decrypt,

                            'encrypt|e=s' => $encrypt,

                            'key|k=s' => $ikey) || ! defined $ikey || defined $help);

            DECRYPT() if defined ($decrypt && $ikey);

            ENCRYPT() if defined ($encrypt && $ikey);

            ######################################

            # sub USAGE

            ######################################

            sub USAGE {

                            print "usage: ./xorbase64.pl [-h] [-k <key>] [-e <string>] [-d <string>]\n";

                            print "\n";

                            print "Options:\n";

                            print "\t-h, --help tprint this help\n";

                            print "\t-d, --decrypt tdecrypt xor/base64 encoded string, needs -k\n";

                            print "\t-e, --encrypt tencrypt string with xor/base64, needs -k\n";

                            print "\t-k, --key tkey for encrypting/decrypting, needs -e or -d\n";

                            print "\t-v, --version tversion\n";

                            print "\n";

                            exit 0;

            }

            ######################################

            # sub VERSION

            ######################################

            sub VERSION {

                            print "Version 0.1 (25.12.2012)\n";

                            exit 0;

            }

            ######################################

            # sub XOR

            ######################################

            sub XOR {

                    my $xor = $_[0]^$_[1];

            }

            ######################################

            # ENCRYPT

            ######################################

            sub ENCRYPT {

                    # split string as hex into array @carray

                    for (my $h=0;$h<=length($encrypt)-1;$h++) {

                            my $chex = substr($encrypt,$h,1);

                            push (@carray,ord($chex));

                    }

                    # split key into array @key

                    for (my $k=0;$k<=length($ikey)-1;$k++) {

                            my $key = substr($ikey,$k,1);

                            push (@key,ord($key));

                    }

                    # encrypting/decrypting string

                    for (my $i=0;$i<=@carray-1;$i++) {

                            $cstring .= chr(XOR($key[$i],$carray[$i]));

                    }

                    # convert to hex & base64 encode

                    my $hex = join '', unpack "H*", $cstring;

                    my $cipher = encode_base64($cstring);

                    # Output

                    print "[+] Cleartext: $encrypt\n";

                    print "[+] Key: $ikey\n";

                    print "[+] Hex: $hex\n";

                    print "[+] Ciphertext: $cipher";

                    exit 0;

            }

            ######################################

            # DECRYPT

            ######################################

            sub DECRYPT {

                    # base64 decode & convert to hex

                    my $cipher = decode_base64($decrypt);

                    my $hex = join '', unpack "H*", $cipher;

                    # split string as hex into array @carray

                    for (my $h=0;$h<=length($hex)-1;$h+=2) {

                            my $chex = substr($hex,$h,2);

                            push (@carray,hex($chex));

                    }

                    # split key into array @key

                    for (my $k=0;$k<=length($ikey)-1;$k++) {

                            my $key = substr($ikey,$k,1);

                            push (@key,ord($key));

                    }

                    # encrypting/decrypting string

                    for (my $i=0;$i<=@carray-1;$i++) {

                            $cstring .= chr(XOR($key[$i],$carray[$i]));

                    }

                    # Output

                    print "[+] Ciphertext: $decrypt\n";

                    print "[+] Hex: $hex\n";

                    print "[+] Key: $ikey\n";

                    print "[+] Cleartext: $cstring\n";

                    exit 0;

            }

            #EOF

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