Abstract:
The stream cipher A5/2 is used in GSM (Global System for mobile Communication) for
authentication and data encryption. There have been numerous successful attacks that
were launched on A5/2 hence breaking down its security. For realizing the LSE solver
component, we used Gauss-Jordan algorithm. Our attack immediately recovers the
initial secret state of A5/2 which is sufficient for decrypting all frames of a session using
a few cipher text frames. We directly attack the GSM speech channel. It requires 16
cipher text frames and completes the attack in about 1 second. With minor changes
also input from other GSM channels can be used to mount the attack.
