A system for encrypting and decrypting data being transmitted between a data processing device and a storage device is provided. The system includes a password storing unit, an input unit, an authentication unit, a read unit, a key generator, an encrypting unit, and a decrypting unit. The password storing unit stores an initial password. The input unit is for receiving a current password. The authentication unit is for determining if the current password matches with the initial password. The read unit is for reading the initial password and an identification number of the system. The key generator is for generating an encrypting key and a decrypting key using the initial password and the identification number. If the current password matches with the initial password, the encrypting unit and the decrypting unit are operable to encrypt and decrypt the data using the encrypting key and the decrypting key correspondingly.