Block ciphers-DES DATA ENCRYPTION STANDARD 曹天杰 Tianjie Cao ticao cumt. edu. cn College of Computer science and echnology, China University of Mining and Technology Xuzhou, China 中国矿业大学计算机科学与技术学院 2003.5.191 曹天杰 Tianjie Cao tjcao@cumt.edu.cn College of Computer Science and Technology, China University of Mining and Technology, Xuzhou, China 中国矿业大学计算机科学与技术学院 2003.5.19 Block ciphers-DES DATA ENCRYPTION STANDARD