My Senior Junior Hacking Correspondent was interested in taking the chip from his Opal card and fitting it into his sonic screwdriver. I couldn’t help but agree that getting on the bus and pointing your sonic screwdriver at the card reader would be enormously cool and so agreed to do some research.
This was all prompted by memories of the London gentleman who placed the chip from the Oyster card inside a wand and walked through the turnstiles dressed as a wizard.
The short answer is that it may be feasible. There’s an nice Instructable on how to go about getting at the innards of an Oyster card by melting the card away with acetone. But there are also recent comments on the Internet saying this has become harder to the point of impossible with more recent versions of the card. I can’t find anyone who has tried to do this with an Opal card.
There’s no theoretical reason that removing the chip and antenna from an Opal card and placing it in something else wouldn’t work. The trick would be removing it intact and then placing it in something else in a way that the antenna still functions fully. Practically achieving those things is going to be tricky especially when the idea is to dramatically change the form-factor. I think it may be feasible, but it’s not a trivial undertaking and you’d probably end up destroying many cards while getting the process down pat.
The other issue is getting pulled up by the bus driver who doesn’t appreciate the beauty of the ‘hack’. As a one-off it’d be amusing and explainable; on an on-going basis it’d just be a pain as mucking about with the card in this way breaches the terms and conditions of use even though you’re not fiddling with the account balance or anything like that.
Is that worth if for the sonic screwdriver approach? Well, almost but probably not. Realistically you’d be better off hiding the opal in your hand while pointing the sonic screwdriver at the reader – less cool, but you get most of the same effect without the pain.
Of course the more practical Opal card hack is to beat the system rather than the card. This does involve running though…