The Research of Parameters Selection on the Model of Time-memory-data Trade-off Attack to A5/1

GSM is the most popular world-wide standard for mobile communication system. GSM uses A5/1 algorithms to protect the users information. It is very important to research the attack of A5/1. In this paper, by analyzing the property of the state space reduction, a model of Time-memory-data trade-off attack to A5/1 algorithms is described, that model based on variable distinguished point and thin rainbow tables. The formulas are derived and the parameters are determined. By using FPGA and parameters determining, the attack success rate exceeds 99% in 1 second on average that improve the practicability of the attack. Based on this model, the method to determine the parameters has reference value to other platform and constraints.