http://www.perlmonks.org?node_id=97075


in reply to Re: A real challenge
in thread A real challenge

or even 
#!perl -w
use strict;

sub encode_decode ($) {
    my $txt = shift;
    my $key = 'Copyright © 2000 ActiveState Tool Corp.' x length $txt;
    my $enc = $txt ^ substr $key, 0, length $txt;
    return wantarray ? unpack "C*", $enc : $enc;
}

undef $/;
my @encoded_ascii = encode_decode <DATA>;    # one or other
#my $encoded_string = ~~encode_decode <DATA>; # of these two

__DATA__
#!"#$%&'()*+,-./0123456789:;<=>?@
#ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`
#abcdefghijklmnopqrstuvwxyz{|}~
#!"#$%&'()*+,-./0123456789:;<=>?@
#ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`
#abcdefghijklmnopqrstuvwxyz{|}~
#!"#$%&'()*+,-./0123456789:;<=>?@
#ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`
#abcdefghijklmnopqrstuvwxyz{|}~
print "Show me the encoding!\n";

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"Argument is futile - you will be ignorralated!"

Replies are listed 'Best First'.
Re3: A real challenge
by bikeNomad (Priest) on Jul 16, 2001 at 20:39 UTC
    You're making $key too long by a factor of 39. You want something more like this (where @encoded is the given byte array):

    my $encodedString = pack('c*', @encoded);
my $key = 'Copyright © 2000 ActiveState Tool Corp.';
$key = $key x ( length($encodedString) / length($key) + 1);
$key = substr($key, 0, length($encodedString));
print $key ^ $encodedString;

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[reply]
[d/l]
      I know - it's just so that the key can be any length without having to do the length X/length y + 1 thing all on one line :) I have to substr it anyway so what's a few bytes between system calls! I wouldn't have been so frivolous if I was getting the key from STDIN though!

      "Argument is futile - you will be ignorralated!"

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