Eavesdropping on cell phone conversations has long been
considered the domain of law enforcement and actors in spy movies. Security
researchers at the 2008 Black Hat conference in Washington, D.C. have unveiled
a new, faster method for eavesdropping that could be built for as
little as $1,000.
Most GSM (Global System for Mobile communications) networks use the 64-bit A5/1 encryption, which
has been cracked in theory for approximately ten years. The major breakthroughs
made by the security researchers David Hulton and "Steve" (who
declined to give reporters his last name), however, is in the cost and speed of
the cracking attempts.
According to the security analysts, a $1,000 GSM-snooping station would be able
to crack the encryption in 30 minutes, and $100,000 worth of equipment would achieve
similar results in 30 seconds. The basis for the technology is the use of
field-programmable gate arrays to pre-compute all of the possible keys – more than
288 quadrillion -- over a period of three months, and then use this massive
amount of data to decrypt GSM communications on the fly.
The vulnerability of the GSM SIM cards was also raised by Mr. Hulton and
"Steve" -- the SIM ID number is broadcast in cleartext, which could
reveal the make and model of handset being used. In conjunction with the
ability to break encryption, this could be used to push an "operator-specified"
application onto the card, or use triangulation to determine the location of
the handset relative to connected towers.
Cell phone users should not begin speaking in code just yet, however, as the
technology is still in development and has yet to be shown beyond a
proof-of-concept. GSM Association spokesman David Pringle also stated that more
advanced encryption is being deployed, and that some current GSM data networks
already use a superior encryption method.