Decrypt Cisco-encrypted passwords in configuration files

#! /usr/bin/perl -p
# Decrypt Cisco-encrypted passwords in configuration files. Perl
# version; requires perl 4.036 minimum. Unlike many similar tools
# circulating on the net, this one also works for passwords longer
# than 11 characters (i.e. doesn't chop after 11 chars and doesn't
# get confused with newer IOS versions which have alleviated this
# limit).
#
# Absolutely no warranties whatsoever. Use at your own risk. No
# batteries included. Not suitable for children under 3 years.
#
# Written and © by Helge Oldach <ciscocrack@oldach.net>
#
# You are not expected to understand this code, although the algorithm
# is really blatantly stupid. Look how short it is in perl.

@tbl = unpack("C*", "dsfd;kfoA,.iyewrkldJKDHSUBsgvca69834ncxv9873254k;fg87");

($pre, $dummy, $seed, $pwd, $dummy, $suf) = ($_ =~ /^(.*\s+(password|md5)\s+)7\s+([0-1][0-9])(([0-9A-F][0-9A-F])+)(.*)$/);

if ($pwd) {
 $_ = $pre;
 foreach $p ($pwd =~ /../g) {
  $_ .= pack("C", hex $p ^ $tbl[$seed++]);
  $seed %= $#tbl;
 }
 $_ .= $suf . "\n";
}

or

join([chr(int(x[i:i+2],16)^ord('dsfd;kfoA,.iyewrkldJKDHSUBsgvca69834ncxv9873254k;fg87'[(int(x[:2])+i/2-1)%53]))for i in range(2,len(x),2)])