1. in [Statutes of the Realm];Raithby,1819
2. [Foundations of Cryptography: Volume I Basic Techniques];Goldreich,2003
3. [Foundations of Cryptography: Volume II Basic Applications];Goldreich,2001
4. [Cryptography: theory and practice];Stinson,2006
5. “Data encryption standard. “National Bureau of Standards (U.S.), Federal Information Processing Standards Publication 46 (1977).