Security researchers Karsten Nohl and Chris Paget presented their findings in a presentation (WMV video) Monday at the 26th Chaos Communication Congress (CCC) in Berlin. A practical demonstration of the vulnerabilities and potential exploits is scheduled to take place at the conference on Wednesday at 12:00 GMT.
The demonstration is a follow-up to a presentation the two researchers made in August at the Hacking At Random conference, during which they outlined serious flaws in the GSM encryption scheme.
GSM is used in approximately 80 percent of the world's mobile communications systems, and in about 3 billion cell phones across the globe, according to industry estimates. In his CCC presentation yesterday, Nohl pointed out that much data has already been published about GSM's vulnerabilities, but the pair's new research takes it one step further -- by showing how GSM calls can be intercepted and decoded using relatively low-cost hardware and open-source software that is readily available on the Web.
"We just wanted to move all of this into the open domain so you can try it at home," Nohl joked.
Using about $1,500 worth of USRP hardware and open-source software called OpenBTS, the pair on Wednesday will demonstrate how a hacker can create a GSM base station that would be powerful enough to intercept mobile phone calls and sophisticated enough to break through the A5/1 encryption algorithm that is currently used in most GSM cell phones.
Some GSM operators had hoped to improve system security through the use of a new algorithm, A5/3, which is part of most of the emerging 3G services. "Even A5/3 -- the better algorithm -- does not increase GSM's security significantly until the security scheme is overhauled more thoroughly," Nohl said.
In the past, some GSM service operators and other experts had stated the hardware and software requirements required for GSM eavesdropping would be too expensive and sophisticated for the average hacker to deploy. In their presentation, Nohl and Paget debunked that argument, outlining methods for using publicly available data, open-source software, and low-cost hardware to develop a hack in a relatively short period of time.
"GSM has been considered insecure for some years -- however, it is a huge development that the theoretical attack on the GSM encryption cipher is now a reality," says Stuart Quick, operations manager at Henderson Risk Ltd., a London-based security and risk management services firm. "There is now a very real and imminent threat that GSM voice communications will be compromised, and users must start to consider how they can increase the security of their valuable/commercially sensitive calls they make."
The demonstration could also cause some companies to consider separate encryption of cell phone calls, according to one vendor that offers such technology. "Our research shows that 79 percent of organizations discuss confidential or sensitive information at least weekly on mobile phones," says Simon Bransfield-Garth, CEO Cellcrypt Ltd. "The news that GSM has been cracked will be very worrying for anybody who discusses valuable or confidential information over their mobile phone."
Organizations should assume that within six months of the demo GSM phone calls will be at risk, says Stan Schatt, vice president and practice director for healthcare and security at ABI Research.
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