Friday, April 18, 2008

FutureWatch - Eavesdropping on GSM Cell Phones

A web service that will make it easy and inexpensive to crack the GSM A5/1 encryption protocol, quickly enough for a call that is still in progress, is slated to launch at the end of April. Living right at the intersection of open hardware, open source software, software as a service, and cryptography, the service will reduce the cost and effort of cracking GSM call encryption by at least an order of magnitude.

The service is being developed by members of the GSM Software Project and demonstrates just how much things have changed in the world since the GSM system was designed. Various approaches to cracking both A5/1 (the European standard) and A5/2 (the weaker US standard) have been available for some time but this one is unique in that it should be available to researchers and hackers at the end of April in hosted api form instead of pdf.

Back in 1997, this overview of the GSM system declared that "Enciphering is an option for the fairly paranoid, since the signal is already coded, interleaved, and transmitted in a TDMA manner, thus providing protection from all but the most persistent and dedicated eavesdroppers." After all, such a radio encoding scheme made the signals invisible to typical radio band scanners.

Today, however, the availability of the Universal Software Radio Peripheral (USRP), an open hardware software defined radio that sells for about $700, combined with work being done at GNU Radio project to codify the GSM waveform (also targeted for the end of this month), makes this once reasonable point of view seem quaint. Good encryption is now a must and it appears that A5 no longer qualifies. (more)