Abstract: By analyzing the weakness in design of the stream cipher Rabbit, we presented key-recovery attack on it, Afto guessing 96bits, 96bits and 5bits in turn, we can obtain the internal variables, the counter variables and the secret keys in sequence. The result shows that precomputation complexity of whole process is O(296)time complexity is O(297)，request memory space is O(295.81).Comparing with existing attack algorithm, it adds precomputation complexity and memory space, but reduces time complexity.

Key words: Rabbit, Stream cipher, Key-recovery attack, Memory space