Some Dutch researchers recently illustrated once again that “security by obscurity” is not a good way to secure systems. Transport for London (TFL) have for some years been running a prepay card system called the “Oyster Card”. The Oyster Card is an RFID card that you wave over a sensor at the start and end of your train trip, which takes money from your prepay account with TFL. Oyster offers a preferential rate, cheaper than paper tickets, and has had a very high take-up rate with London commuters and residents.

However, the system has now been cracked. At the heart of the Oyster card is a chip called the Mifare Classic, which uses a secret algorithm. Some Dutch researchers decided to target this system, and have discovered how this works. As a demonstration, they used their knowledge to create their own card, which they used to travel around free on the London Underground for a day.

Their interest in the Oyster Card probably stems from the fact that the same Mifare Classic chip is also used in access cards used to secure Government buildings in the Netherlands. In a rather nice demonstration of the separation of powers working in a democratic country, they now have leave from a Dutch judge to publish details of how the Mifare algorithm works, which they will be doing at a security conference in the coming October. This would not have been the outcome that the Dutch government would want, since they now have to take extra steps to secure buildings with more security personnel.

But “hushing the problem up” is not a solution in the security world. The problems don’t go away when you punish the researchers. For every ethical hacker there are probably another two Black-Hats who want to sell the information to those that could profit from free travel in London, or access to Dutch Government property.