Attack of the clones

Hackers can clone mobile phone SIM cards in minutes, and make calls at their victims' expense.

In theory, at any rate: IBM researchers have uncovered a process, dubbed partitioning attacks, which lets crackers extract secret key information from SIM cards by monitoring side-channels, such as power consumption and electromagnetic emanations.

This is much easier than breaking the cryptographic algorithms used by the card or using intrusive attacks to extract the key from the microchip. According to IBM, key information can be extracted in minutes using partitioning attacks - against hours needed for older attacks.

Codebreaker

Some information about the internal working of computing devices can be derived by looking at power consumption and electromagnetic emanations. This is well known.

Many chip cards which perform cryptographic algorithms are designed to resist such information leakage. SIM cards deployed in many GSM networks use the COMP128 cryptographic algorithms or its derivatives for user identification and for achieving communications and transaction security.

The IBM Research team discovered a new way to quickly extract the COMP128 keys in SIM cards using side channels - despite existing protections. The COMP128 algorithm requires the lookup of large tables, which is achieved only in a complicated way on simple devices, such as SIM cards, so that sensitive information can leak into side channels.

Because of this an attack is accomplished easily by making the card perform the algorithm just seven times with the unknown key, IBM researchers say.

To combat this, IBM has designed a way of protecting table lookup operations from side channel attacks.
IBM say this is easy to implement in cell phones as the proposed technique uses little RAM for the ancillary table.

Cell phone users can also protect themselves against such attacks by taking precautions such as: not lending their phones to strangers; or leaving them unattended.

A technical paper on IBM's work, Partitioning Attacks: Or how to rapidly clone some GSM cards, by Josyula R Rao, Pankaj Rohatgi, Helmut Scherzer and Stefan Tinguely will be presented at the IEEE Symposium on Security and Privacy, in Oakland, California next week. ®

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External Links

Summary of IBM's research on GSM cell phones ID card hacking
More detail on IBM's security research