In recent years, people have begun paying more and more attention to the protection of the software. Besides legal means, software developer should stress on technical means to protect their own property rights and interests. Software encryption techniques is the way. To protect their own development and research results, computer software developers often want to do software encryption. Early use of encryption methods (such as hard disk encryption, encryption card, etc.) are eliminated, because of all kinds of defects. Instead, encryption technique of softdog is an arising ideal means of encryption in recent years.
The design and implementation of software has no stereotyped pattern, people can develop and do at their own wise way. And this presents the value of softdog encrypting system. This thesis introduces one kind of super softdog technique. It utilizes the plug-in encryption facility of PC LPT and private encryption procedures to achieve the passwords input, preservation, reading and proof. It has 2 parts of passwords, input codes and return codes. Input codes is from encryption software of PC, and return codes is from input codes & the internal software of SCM. This encryption method is a more confidential, of much more password broken difficulty and can be applied to many different software systems, and other excellent features.
Keywords: Softdog , PIC MCU, Encryption, Parallel port, Decryption
