Abstract:The bluetooth combiner, a combiner with four bit memory, is the stream cipher used in bluetooth protocols. The expression and computation of correlation coefficients between inputs and outputs of this combiner is difficult, while this is the base of correlation analysis and correlation attack to it. In this paper, the formulas for correlation coefficients and conditional correlation coefficients of general combiners with memory are presented, with which the coefficients can be computed fast. By using these formulas, all kinds of correlation coefficients ofbluetooth combiner are computed, and some results are list in the paper.