On an improved summation generator with 2-bit memory

The summation generator is a real adder generator with a maximum period, near-maximum linear complexity and maximum order of correlation immunity. However it is neither secure against and nor immune to correlation attack between its output sequences and carry sequences in special cases. A modi"ed summation generator, secure against such an attack, has recently been proposed, but no proof is given about its period and linear complexity. In this paper, we propose a new modi"ed summation generator immune to correlation attack. Moreover, we conclude that its period is maximum and that its linear complexity is the same as that of the original summation generator. ( 2000 Elsevier Science B.V. All rights reserved.