An information processing system comprising interface circuitry configured to receive message-independent information, the message-independent information having been generated by another apparatus and transferred to the interface in advance of a digital signature being generated, send message-dependent information to an external device, and receive a digital signature from the external device; and processing circuitry configured to generate the message-dependent information from a message and at least a part of the message-independent information, and associate the digital signature with the message.