Along with the extensive application of the networks, networks security has become a very important issue which affects the efficiency of internet substantially, thus internet security is poorly needed. A reliable internet information system shall ensure the transmitted information completed, confidential as well as unchangeable. Nowadays there are many kinds of security technologies for communication and networks information transmission, the core technological element is the so called data encryption. Message encryption techniques are also a crucial element of the cryptograph in modern times. There are mainly traditional cryptographic key encryption systems, and public cryptographic key encryption system which is developed based on data encryption technology. Public cryptographic key encryption system is widely applied in data encryption and digital signature.Up to now the information security technology research in China has experienced two phases: communication secrecy,computer data protection. We are just moving to the third phase which is called networks information security research. There is still a big gap between the level of China's technology and that of developed countries and especial in areas of system security and security agreement due to late commencing, less investment, unfocused approaches. This is a huge challenge to have our own innovative information security theory and algorithms. However we shall also know that China has set up certain basis for networks information security research, this is epically true in the field of research on cryptogram.Although some office automation systems, such as telephone, fax are very broadly used in various Chinese governmental agencies, the application of modern office automation systems is not yet prevalent, thus many documents are still circulated and read in hard-copies. This wastes lots of time and money. Modern office system mainly based on networks is gradually in place with the theological and economic development in China, this trend and movement make information security more important than in the past.The trends of cryptography and commonly used algorithm of data encryption are first introduced in this article, and a encryption of RSA,MD5 and DES encryption or decryption has been developed .