INFORMATION PROCESSING DEVICE, MOBILE DEVICE, AND COMMUNICATION SYSTEM

The present disclosure relates to an information processing device, a mobile device, and a communication system capable of updating a session key. A first secret is derived from a key schedule by using first communication including transmission or reception of a command for controlling second communication faster than the first communication or a response to the command, a first session key related to the first secret is derived, the first session key is used for encryption or message authentication of the first communication, a second session key is received, transmitted, or derived by using the first communication, the second session key is used for encryption or message authentication of the second communication, a third session key is received, transmitted, or derived by using the first communication, and the third session key is used instead of the second session key. The present technology can be applied to, for example, a communication system conforming to the MIPI standard.