The CueCat is a nifty little piece of
hardware. It's an optical barcode reader that plugs into your PS/2 port.
Simply swipe the glowing red "mouth" of the reader across a standard
barcode, and the output is fed into your computer via the keyboard
How much would you expect to pay for one of these cool toys? $30? $15? $7?
The answer? Nothing! You may be asking "How'd you manage that?", but it's
actually quite simple. Go to your local Radio Shack, walk up to a clerk,
and simply say "Hi! I want a CueCat!" (If they give you a blank stare, say
"You know, the barcode thingie.") The clerk will say "Cool!", and proceed
to hand you a Special Radio Shack catalog (with barcoded item identifiers),
and a bag containing a CueCat CDROM, instruction guides, and the Barcode
Reader. Give the clerk some information (name, address, etc.), and you
walk out with a free barcode reader! (Note: This
information is no longer valid, as RadioShack no longer distributes the
CueCat, and Digital Convergence has pretty much gone out of business.
Now, the dilemma. What do you do with your new found toy?
The idea of the product isn't a bad one. The software that comes with the
CueCat reads the barcodes you scan, connects to the main server, and
compares the barcode you scanned with the ones present in its database. If
it finds a match, the software will kick you to the cooresponding website.
So say you're drinking a Pepsi. You scan the barcode off the bottle, and
your computer connects you to Pepsi's website. The system recognizes
thousands of barcodes, and knows the relevant websites. The bad part, is
that each scanner is assigned a unique serial number. When you install the
CRQ software, you are given a unique "activation" number. These numbers are
attached to you, and your name floats around as a candidate for targetted
advertising and Gestapo habit-tracking. Screw that.
We're not interested in the software. (Mine hasn't even been opened.) We're
interested in the neat little reader, and the unlimited possibilities that
When you connect your reader, open up a text editor and scan a barcode.
You'll see something like this:
The output isn't what you expected, is it? That's because there's a lot
more information in there than a simple 12 digit number sequence. The output
isdivided into 3 sections, seperated by periods.
The first (and usually longest) section is your unique serial number,
assigned to your CueCat. This string never changes, regardless of what you
scan. An ALT+F10 Signal preceeds the serial number, as a "wake-up call" to
The second string defines the barcode type. There are many types of barcodes
out there, from UPC and its variants, to ISBN, EAN, and others. This is
the part of the output that identifies which type it is.
The third, is the barcode data itself. The reason it's not simply a numeric
sequence, is because the makers of the CueCat didn't want their toy to be
used for reasons other than its intended purposes. So they implemented a
weak "string substitution" style of encryption. (In reality, base64+XOR)
Give a geek a cool toy, and he will play with it. Give millions
of geeks the same toy, and it evolves into a new toy.
How to Decode
So we geeks started digging deep into how the scanner works. The
"encryption" was cracked in very little time, and software has been
developed to decode the scanner's output. Let's look at our above
This is the result of a barcode scan from a cup of Oreo YoCrunch Yogurt.
The actual barcode reads:
0 46675 00080 8
Ignore the first string from the scanner output, as that's the serial
number. The second string defines this as a UPC-A Barcode, however that
is unimportant in the decoding process. To decode the third string,
use this chart as a reference:
A B C
0 | C3 n Z
1 | CN j Y
2 | Cx f X
3 | Ch b W
4 | D3 D 3
5 | DN z 2
6 | Dx v 1
7 | Dh r 0
8 | E3 T 7
9 | EN P 6
Break the final string into the matching patterns from the chart, and you
get the following:
C3 D 1 Dx r 2 C3 n Z E3 n 7
Now, simply plug in the numbers from the left side of the chart, replacing
the cooresponding pattern.
0 4 6 6 7 5 0 0 0 8 0 8
Whee! We see it matches the original barcode.
March 27, 2003
Added a note indicating you cannot acquire the CueCat from RadioShack
February 15, 2002
I've rewritten this page to conform with Accipiter.org's current style.
September 29, 2000
I've been adding minor contributions to CueCat development, and now it's
time for one a bit bigger. I have written a script for
The mIRC IRC Client that decodes the
CueCat output. This is a totally inefficient way of decoding, and I
know there's a better way of doing it. However, this script DOES
work, and it works fairly well. You can download it in the "Software"
section of this page.
• UPDATE: Whoops! I found a bug! Some strings for
the number '8' weren't decoding properly due to the order of the string
substitution in the script. The problem has been corrected in version 1.1.
• UPDATE: Silly Me. The mIRC Editor will NOT load
the script! The formatting for the INI file was incorrect in versions prior
to 1.2. This problem has been fixed in 1.2. My apologies. (Wow! 3 versions
in one night. Sheesh.)
September 26, 2000
For some time now, the people over at Digital Convergence (the makers of the
CueCat) have been sending out legal notices to website owners who have
hacked their CueCat. They claim that these websites are infringing on their
Intellectual Property. To preserve the variety of software out there for
the CueCat, I've started distributing it on this page. If you have developed
a piece of software that you would like to be mirrored here, or if you want
me to link to your CueCat project page, please feel free to
mIRCue is a CueCat decoder that I have written for the mIRC IRC Client.
Download mIRCue Version 1.2
Download mIRCue Version 1.1
Download mIRCue Version 1.0
CatScan.txt - A Perl Script that
decodes the output, by Andrew
curcatd1.0.zip - Another decoder
written in perl, by Kevin Fowlks.
DeCue.txt - Larry Wall's (remarkably short!) Perl Script decoder.
cuecat-0.1.4.tar.gz - The
Linux Kernel Patch for the CueCat, by Pierre-Philippe Coupard.
KittyCode - A decoder written in
Cat.txt - Yet another Perl decoder, by
cuecatvb.zip - A CueCat Visual Basic
decoder application by Graf
Reiner, with bugfixes by Doug