Back in August, [h1kari] presented an analysis of the A5 crypto spec used in GSM systems. Almost all GSM conversations in the US and Europe are encrypted using this standard. At the time they were still in the planning stages of building their rainbow table of shift register states. Today we heard an update on the progress. The whole space is 2^58 in size and would take a standard PC 33,235 years to calculate. Not being patient people they built a box containing 68 express card based FPGAs. Each one is capable of doing 72 billion operations per second. So far they’re one month into the 3 month process. Once the table is completed any person can crack a GSM conversation in 30 minutes using 1 FPGA and the 2TB table. They do have plans for building an optimal system that would be based on solid state drives and 16 FPGAs that should do the crack in just 30 seconds.
ShmooCon 2008: Intercepting GSM Traffic
February 15, 2008 By 17 Comments