Parallel decomposition of nonautonomous 2-linear shift registers

A variant of decomposition of nonautonomous 2-linear shift register over the Galois field is considered. It is shown that a nonautonomous 2-linear shift register over the finite field may be represented as a parallel system of clock-controlled shift registers. By means of this construction and the meet-in-the-middle attack the estimate of the cryptographic security of the register considered is lowered considerably.