With SMSecurity, any kind of big capacity file can be split into several small ones with appointed capacity. In this way, it is easy to communicate or share the big files on the Internet, or to copy them with small capacity discs. The person who receives the split files just merge the files, so communicating, sharing and copying of big capacity files can be achieved. During the split and merge, the split files can be encrypted (128 bits), decoded, and tested, making data in the files keep completed and safety.