An architecture for software integrity assurance

The work described in this paper refers to the CASS (Computer Architecture for Secure Systems) architecture previously reported by Mohay et al. (1993) which addresses the problem of software authenticity on two fronts. Three prototype implementations of that architecture have been developed, two of these at the kernel level targetting UNIX SVR4.2 and the Mach 3.0 Micro-Kernel, while the third-for reasons of generality-has involved the implementation of a specialised shell which is then portable across UNIX-style platforms in general. Before executing an applications program, these implementations verify the integrity of a program seal associated with the application. If verified, this provides assurance of program compliance with safety criteria previously checked and certified by our secure Modula-2 compiler and linker. The paper describes how our Modula-2 based development environment has been modified to provide the cryptographic seals required and exploited by the CASS kernels and the CASS Shell software to provide integrity assurance