March 14, 2008 (Computerworld) A student at the University of Virginia has discovered a way to break through the encryption code of RFID chips used in up to 2 billion smart cards used to open doors and board public transportation systems.
Karsten Nohl, a graduate student working with two researchers based in Germany, said the problem lies in what he calls weak encryption in the MiFare Classic, an RFID chip manufactured by NXP Semiconductors. Now that he's broken the encryption, Nohl said he would only need a laptop, a scanner and a few minutes to get the cryptographic key to an RFID door lock and create a duplicate card to open it at will.
And that, according to Ken van Wyk, principal consultant at KRvW Associates, is a big security problem for users of the technology.
"It turns out it's a pretty huge deal," said van Wyk. "There are a lot of these things floating around out there. Using it for building locks is the biggy, especially when it's used in sensitive government facilities — and I know for a fact it's being used in sensitive government facilities."
Van Wyk told Computerworld that one European country has deployed military soldiers to guard some government facilities that use the MiFare Classic chip in their smart door key cards. "Deploying guards to facilities like that is not done lightly," he added. "They recognize that they have a huge exposure. Deploying guards is expensive. They're not doing it because it's fun. They're safeguarding their systems." He declined to identify the European country.
Manuel Albers, a spokesman for NXP Semiconductors, said the company has confirmed some of Nohl's findings. However, he said there are no plans to take the popular chip off the market.
"The MiFare chip was first introduced in 1994. At the time, the security level was very high," he said in an interview. "The 48-bit key lengths for encryption was state of the art."
Albers added that the company has other, more secure chips in its product portfolio these days, but the MiFare Classic is a relatively inexpensive, entry-level chip. Anyone needing a highly secure smart card should make sure there's layered security and not just depend on the chip's encryption, he said.
"We have to start this discussion, really, at the level where we differentiate between the security level the chip provides and the additional security features an entire card provides. You're dealing with a layered security system, like strands to a rope," said Albers, noting that between 1 billion and 2 billion smart cards with this MiFare Classic-type chip have been sold. "As long as there's demand for this product [and] system integrators saying this product is good enough for their platforms, we will continue to offer it."
Albers noted that NXP recently released MiFare Plus, which is backward-compatible with the MiFare Classic while offering better security. He said the company did not release the updated chip because of Nohl's findings, but it did use some of his information when designing it.
"The problem is the card and the card reader," said Nohl. "They speak the same cryptography language that is flawed. Both need to be replaced. There is a lot of infrastructure to be replaced. The encryption is not standard. It's weak. It uses two short keys."
While Albers said "the majority" of the smart cards with this chip are used as bus or subway cards, both van Wyke and Nohl said the real problem lies in the cards that are used as door locks.