Cryptanalysis of a chaos block cipher for wireless sensor network

Based on the analysis of a chaos block cipher for wireless sensor network (WSN), it is found that there is a fatal flaw in its security because the number of rounds is too small and the calculation precision of round function is too short. The scheme could be cryptanalyzed by utilizing differential cryptanalysis theory. First, the third round key is recovered by chosen plaintext attack according to the characteristics of the round function. Then, the second round key can be deduced from the relationship of the sub-keys between the second and the third rounds. Based on the above successful attacks, the first round key could also be broken by brute-force attack. Finally, by employing the characteristics of Feistel structure, the fourth round key could also be obtained. Since all round keys have been cryptanalyzed, the plaintext can then be decrypted. The encryption scheme is proven to be insecure consequently.