Tuesday, October 4, 2011

Mifare DESFire MF3ICD40: Death by Side-Channels

Definitively the best and the most practical talk at CHES 2011 was given by David Oswald. The work has been descried in the paper titled "Breaking Mifare DESFire MF3ICD40: Power Analysis and Templates in the Real World" by David Oswald and Christof Paar both from Ruhr-University Bochum and concerns practical attacks on contactless smardcards.

So what has really happened? Authors performed non-invasive side-channel attacks on aforementioned types of smartcards, which means that they were able to reveal full 112-bits key from a card. This allows to modify, read out and clone content of an attacked smartcard very easily.

So why is it so important? Firstly, this is another (after side-channel attack on KeeLoq) practical attack on a device widely deployed on all over the world and also (according to the authors) the first available in an open literature template attack performed on real a world device. Mifare DESFire MF3ICD40 is a 3DES alternative for Mifare Classic (reverse-engineered and then broken) which is widely used in mobile payments and in access controls, e.g., by Czech railways (in-karta) or in San Francisco (Clippercards). Secondly, to perform a non-invasive power attack and a template attack on contactless smartcard, David and Christof used low cost equipment which cost is estimated to be $3000 and computational time of a few hours. That means that a key can be reveled by an attacker having a side-channel knowledge and practical skills.

The presented paper shows once again that side-channel attacks are not only theoretical, performed in labs on well-known designs, but might be applied to black-box devices and so might have a big impact on real world security.

Goodbye Mifare DESFire MF3ICD40, welcome Mifare DESFire EV1 ...

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