by Andrew Munchbach on December 9th, 2009 at 1:04pm
Filed under: GSM, News 21 Comments
It has been long argued that the A5/1 encryption standard used to secure GSM traffic from eavesdropping is, in fact, insecure, and California based security firm H4RDW4RE is pioneering an effort to hammer that point home by cracking the encryption scheme. The A5/1 cipher is based on a 64-bit key — each cell phone has a 64-bit secret key which is also known by the connected GSM network. When you initiate a call the GSM network uses the secret key to generate a session key and encrypt your phone call. H4RDW4RE’s approach will be to crack this session key using a compressed and custom version of the A5/1’s 128-petabyte code book. Yikes. The aim of the project is to: take the vast code book and compress it down to around 2 or 3 terabytes of data, organize the data into rainbow tables, have these tables searched by a free P2P open-source program (much like SETI@home) in order to cipher session keys. Session keys will, theoretically, provide the ability to decrypt and listen in on GSM phone calls. H4RDW4RE’s goal is to push GSM vendors to finally admit that the technology is flawed and move to the more secure A5/3 code book, which is a 128-bit cipher, and already used by newer cellular technologies such as UTMS. Pretty powerful way to send a message, it sure does beat a letter writing campaign… Hit up the article for more details about the project.