Proposed Enhancement of A5/1 stream cipher

A5/1 used in GSM to encrypt the conversations. In this paper, proposed an enhancement of A5/1 is add fourth register will be increase the total security of proposed algorithm and apply a new filtration functions on each register to strengthen the linear combination function (XOR) with remain same the total number of bits of A5/1 are 64-bits. A5/1 is considered an efficient implementation of hardware. This proposed take efficiency implementation of hardware of A5/1 to produce an algorithm with more high security, also efficient in hardware implementation. The security of generated key will measure by using NIST tests and berlkamp-Massey algorithm.