Alex Biryukov, Adi Shamir and David Wagner showed that they can find the A5/1 key in less than a second on a single PC with 128 MB RAM and two 73 GB hard disks, by analyzing the output of the A5/1 algorithm in the first two minutes of the conversation.
Ian Goldberg and David Wagner of the University of California at Berkeley published an analysis of the weaker A5/2 algorithm showing a work factor of 2^16, or approximately 10 milliseconds.
Elad Barkhan, Eli Biham and Nathan Keller of Technion, the Israel Institute of Technology, have shown a ciphertext-only attack against A5/2 that requires only a few dozen milliseconds of encrypted off-the-air traffic. They also described new attacks against A5/1 and A5/3.
