Divide-and-conquer attack on chaotic stream cipher

A chaotic stream cipher,presented by reference [2],is studied.It is found that the firstly several key stream bits are not sensitive to the least significant bits of the key.A divide-and-conquer attack on the stream cipher which could decrease entropy of the key efficiently is proposed.When the length of key is 128,the success rate of the divide-and-conquer attack is 0.9498 and the average complexity is less than 279.