With the development of information and digitized society, people’s cognition about safety to information and importance of secrecy improve constantly, today, encryption plays an extremely important role on all respects of social life, it is a cross discipline with its corresponding cryptography , it is a applied mathematics discipline to a great extent, Cryptography include many kinds of mathematics knowledge, such as number theory, algebra, the complexity of calculation theory and combinatorial mathematics.
Data encryption standard (DES) is a algorithm that NBS collected publicly used for government department and folk to encrypt computer datum, its purpose is suffice to the demand of the development of the communication network of the computer to the safety and secrecy, security and compatibility of the same level of the implementation system, and reduce the cost of the data encrypted productions at the same time , appearance of DES cryptography is a important incident of history, it cryptography first apply commercial datum keep secret, open password algorithm extensively in history, it starts the precedent of the open password algorithm.
This study has introduced cryptography and relevant theory knowledge, history, current situation and principle of the ones that have narrated DES and encrypt the algorithm briefly. Have introduced the mathematics foundation encrypted; Have explained in detail that DES encrypts the principle of the algorithm; Purpose of design, function realized and every steps of detailed designs of system that detailed explanation DES encrypts, and the result to system testing. The part of the appendix has main source code that DES encrypted the system.
Key word: Data Encryption Standard (DES); Encrypt; Key.