Security problems for a pseudorandom sequence generator based on the Chen chaotic system

Recently, a novel pseudorandom number generator scheme based on the Chen chaotic system was proposed. In this study, we analyze the security weaknesses of the proposed generator. By applying a brute force attack on a reduced key space, we show that 66% of the generated pseudorandom number sequences can be revealed. Executable C# code is given for the proposed attack. The computational complexity of this attack is O(n), where n is the sequence length. Both mathematical proofs and experimental results are presented to support the proposed attack.