>> Now I'm thinking... it appears to be a standard Data Matrix barcode, 
>> so if I could figure out WTF the data encoded in it is, I could print 
>> as many of them as I like, without a fee...
> 
> Won't they encode a serial number in there? As soon as they detect a 2nd 
> stamp in the system with the same serial number (or with one they know 
> they haven't sold yet) there will be trouble.

Yeah, this is probably the main problem. If they know which numbers 
they've actually sold and which ones have actually been used, there's 
not much you can do.

> Also it probably has some checksum, you'd need a shed load of stamps to 
> figure it out probably.

Well, if you were going to reverse-engineer it, sure. But if you could 
figure out the algorithm...

It's like Windows license keys. Each one is a 20-character alphanumeric 
string. There must be some algorithm that Windows uses to decide whether 
the key you just entered is valid. If you somehow knew what that 
algorithm is.......

> And hope they don't encode your IP address or payment details in there too.

If you *knew* how they generate the barcode, you could put an arbitrary 
IP address in there. (Besides, knowing somebody's IP address doesn't 
really tell you a whole heap.) Payment details might be more fun...

> A bit like that system on Blu-Ray discs, where every player plays back a 
> very slightly different version, so when someone rips and uploads to 
> BitTorrent, they can tell exactly which player it was ripped from.

Really? That's news...

Post a reply to this message