LOGICALLY SAFE PROCESSOR SYSTEM

摘要

A dual privilege level coprocessor (20) especially suited for use in a software asset protection system comrises a supervisor processing element (201) and an application processing element (240) coupled by a bus (250). A high privilege read only memory (241) and a secure random access memory (240) are enabled only in response to dedicated control signals from the supervisor processor (210). While an application processor (247) has many general purpose computing capabilities, it is incapable of executing input or output operations. An input/output device (247) is also coupled to the bus and controlled by the supervisor processor. A secure random access memory (246) is provided for storage of sensitive information such as decryption keys. The coprocessor implements a low privilege level of operation for the purpose of executing protected software which is first decrypted under the control of the supervisor processor and then stored in the application processor random access memory (243). The coprocessor is also capable of high privilege operation either by the supervisor processor alone or with the supervisor processor controlling the application processor and its associated high privilege read only memory (241).