Abstract: The security of block cipher SNAKE (2) against Square attacks was re-evaluated．The wrong 5-round Square distinguisher based on equivalent structure given in paper [4] was pointed out．A new 6-round Square distinguisher based on both the structure of SNAKE (2) and its equivalent structures was proposed．Using the new 6-round Square distinguisher,Square attack was applied to 7,8,9-round SNAKE(2) to recover some information of the equivalent key．The time complexities are 212.19,221.59,230.41 respectively,and the data complexities are 2⁹,29.59,2¹⁰ respectively．The results are better than the Square attack given by paper[4]．

Key words: SNAKE,Square attack,Distinguisher,Complexity