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Are GSM Mobile Phones Insecure?

Researchers claim to decrypt messages from the world's most popular mobile phones.

By Ann Harrison, Computerworld   

Alex Biryokov and Adi Shamir published a paper this week describing flaws in an algorithm used to scramble allegedly private conversations on GSM cell phones, which are used by more than 215 million users worldwide. The researchers wrote that a PC with 128MB of memory and large hard drive can break the A5/1 GSM algorithm in less than one second.

The source code for the A5/1 algorithm, which is one of four cryptographic algorithms in the GSM standard, was developed in secret and never published.

In the U.S., GSM is used in the Digital PCS networks of telecommunications companies including Pacific Bell, Bell South, and Omnipoint Communications Services.

The paper, which builds on earlier attempts to break the standard, reportedly describes flaws in the A5/1 algorithm used to secure GSM voice and data transmissions. Voice-encryption algorithms encrypt the voice signal between the cell phone and the base station, but don't encrypt the signal end-to-end within the phone network.

The A5/1 algorithm can be broken if the call is intercepted. However, the Dublin, Ireland-based GSM Association insists there is no hardware capable of intercepting a call. Equipment claiming to intercept GSM transmissions has been offered for sale on the Internet but is now illegal.

The findings of Biryokov and Shamir's paper, which is still being evaluated by the GSM Association, will be discussed at the next meeting of the GSM security working group on December 16.

For more enterprise computing news, visit Computerworld. Story copyright © 2011 Computerworld Inc. All rights reserved.