COMPREHENSIVE SOFTWARE PROTECTION SYSTEM

An efficient software protection scheme is presented in which a data processing system provides comprehensive software protection using hardware and software measures. Specifically, it provides protection of the pattern of access to memory during execution of a program and also provides protection of the data stored in memory. The protection scheme is secure in the sense that it behaves like a black box which reveals no information other than the I/O behavior and running time. Thus, not only the values stored in the general purpose memory are hidden, but also the sequence in which memory location are accessed during execution is hidden. This comprehensive scope of protection is achieved by an extremely efficient scheme. In particular, if the running time of the original program it T, the running time of the protected program is only slower by some factor of (logT).sup.C where C is a small constant.