A 128K EPROM using encryption of pseudorandom numbers to enable read access

A 128K EPROM with a pseudorandom number generator and encryption circuits has been produced to provide a barrier to software piracy and to prevent unauthorized access to computers. The EPROM, known as the Keyed-Access EPROM, is capable of locking its array so that unauthorized users cannot read its contents. An authentication handshake is used to ensure that only authorized legitimate users can open and read the information that is stored in the memory. This unlocking process uses an on-chip pseudorandom number generator, encryption circuitry, and a 64-bit secret key. The security provided by this novel integrated circuit is shown to be effective. The circuit design of the pseudorandom number generator and the encryption circuitry is explained in detail. Several examples of applications are given.