Automatically generated cryptographic functions for renewable tamper resistant security systems

摘要

A secure cryptographic function is generated from a template containing static program code that is the same for all mobile agents and dynamic program code which differs for each function. The dynamic code implements a stream cipher encryption algorithm that is used to encrypt messages processed by the function. The dynamic code may also generate a message digest that is attached to each message. The message digest may be a hash function applied to the dynamic code and, optionally, to the message. Each function may be assigned a limited lifetime, either by assigning it a fixed termination time, a maximum number of messages that it may send or, if the cryptographic function is used with a mobile agent, a maximum number of hosts that it may visit. Any received messages that have been processed by the encryption algorithm after the expiration of its lifetime are ignored.