Cryptography using modular software elements

• Authors: Herbert S. Bright;Richard L. Enison
• Venue: AFIPS '76 Proceedings of the June 7-10, 1976, national computer conference and exposition
• Year: 1976

Protection of information within a computer/communication system can be provided through reversible cryptographic transformation of the information itself into a form that can be returned to usable form only through use of control information known as "key." It is not necessary, in order to achieve access control, that the encryption algorithms, random number generator, or system organization be kept secret; in fact, a basic requirement of modern cryptographic technology is that it must be effective although a would-be penetrator is assumed to have full access to all of that information and the facilities and competence to apply it. Only the key can be assumed to be, and must be, physically secure. The building-block approach outlined makes use of pre-programmed software elements for providing all specialized algorithms, including the Proposed Federal Data Encryption Standard (DES), together with necessary nonnumeric generalized support routines for use with application programs written in conventional procedural higher languages (FORTRAN, COBOL, etc.). Both Strong Algorithm and Long Key methods can be used as required by security-level-vs-cost tradeoff considerations. This method is useful in conjunction with specialized hardware; for testing of programs and hardware; in some cases instead of hardware; and can support multiple-level security applications. The entire scheme, including the Tausworthe-Lewis-Payne bitwise linear recurrence modulo 2 quasirandom number generator, is based irrespective of hardware type on a standardized 64-bit data element.