Abstract: A method and apparatus for privately retrieving information from a single electronic storage device (e.g., a database) is described. An inquiring processor identifies a portion of a database memory with information for retrieval and encodes address of the information into a preselected mathematical function that conceals the identity of the selected information from the database. The inquiring processor transmits the encoded function to the database. The database cooperates by executing the encoded function on the database and transmits an encoded result that represents an evaluation of the encoded function to the inquiring processor. The inquiring processor, having knowledge of the selected mathematical function, decodes the encoded result to generate the information from the selected memory section of the database. The inquiry can be repeated until the inquiring processor can retrieve the selected information.

Abstract: 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.