Security issue (real example)

Real Time Cryptanalysis of A5/1 on a PC (Alex Biryukov and others)
(from seconds to minutes)

A5/1 (less than 2^54 - exhaustive key search)
A5/2 (less than 2^16 - exhaustive key search)

False Base Stations

IMSI Catcher (law enforcement)
and voice catcher (intercept auth)