IEEE802.15.4 ESPARSKey (Encryption Scheme Parasite Array Radiator Secret Key)

Abstract

When the transmission and reception locations of radio waves are different, the correlation of the radio wave propagation characteristics decays quickly. On the other hand, reciprocity of the radio wave propagation holds between two stations that can communicate with each other. Therefore, by making use of the information on the variation of the propagation path, it is possible to generate and share a secret key that cannot be eavesdropped by a third party at a different receiving location. Hence, a secret key generation and agreement system that does not require key management and key distribution can be realized. Also, the ESPAR (Electronically Steerable Parasitic Array Radiator) antenna, under development as a commercial antenna with a variable radiation pattern, can control its directive characteristics by the use of varactor diodes to change the capacitance. Therefore, it is possible to intentionally change the radio propagation characteristics significantly. This paper reports successful test development of a wireless secret key agreement system making use of the fluctuation of the radio propagation characteristics by means of an ESPAR antenna. Further, in a verification experiment using the test system, the key generation success probability was more than 99.998% when a 128-bit secret key was modified every 3 seconds. It is also confirmed by the correlation characteristics with an eavesdropping station that more than 7.19×104 years would be required for the eavesdropping station to decipher the secret key. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(12): 31–44, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20305