The Mitre Corporation

David Gervais

Nicholas C Donnangelo

Jeffrey Minch

Joseph J Rushanan

Marvin D Drake

Christophe F Bas

Daniel Jacob Townsend

Substantially identical numerical sequences known only to stations A and B are generated in a manner not subject to duplication by an eavesdropper and not subject to cryptanalytic attack because they are not derived using a mathematical function (such, as for example, factoring). The sequences are independently derived utilizing a physical phenomena that can only be 'measured' precisely the same at stations A and B. Signals are simultaneously transmitted from each station toward the other through a communication channel having a characteristic physical property capable of modifying the signals in a non-deterministic way, such as causing a phase shift. Each signal is 'reflected' by the opposite station back toward its station of origin. The effect of the communication channel is &#x201c;measured&#x201d; by comparing original and reflected signals. Measured differences are quantized and expressed as numbers.

Generating identical numerical sequences utilizing a physical property and secure communication using such sequences

In a fixed delay optical communication system, rate adjustable differential phase shift key (DPSK) techniques eliminate the need for multiple comparing modules, each corresponding to a different data rate. Setting alternative data rates at integer multiples of the fundamental data rate of the optical communication system allows the system to process the respective integer number of symbols per period of the system, wherein the period of the system is the inverse of the fundamental data rate. Pulse carving techniques may be used to set the duty cycle of clock levels associated with a clock signal. The clock levels may be combined with respective symbols to provide optical symbols having a duty cycle less than 100%.

Rate adjustable differential phase shift key (DPSK) modulation

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Norwood, MA, United States of America

David Gervais