Patent ID: 7603567

Claim:
An information processing system comprising: a potential detection section which detects a predetermined potential applied to a serial bus terminal; a power supply section which supplies the predetermined potential to each component part as a source potential upon detection of the predetermined potential by the potential detection section; an information detection section which detects command information from an external device supplied to the serial bus terminal; a determining section which determines a key operation mode for performing a process in accordance with at least operating information supplied from an operation switch operated by a user arranged on a body, before the information detection section detects the command information and after the potential detection section detects the predetermined potential, and which changes the key operation mode to a command operation mode for performing a process in accordance with the command information supplied to the serial bus terminal, after the information detection section detects the command information; and a processing section which executes one of an encryption process and a decryption process in accordance with the operation mode determined by the determining section.