With the rapid spread of various mobile terminals in our society, theimportance of secure positioning is growing for wireless networks inadversarial settings. Recently, several authors have proposed a securepositioning mechanism of mobile terminals which is based on the geometricproperty of wireless node placement, and on the postulate of modern physicsthat a propagation speed of information never exceeds the velocity of light. Inparticular, they utilize the measurements of the round-trip time of radiosignal propagation and bidirectional communication for variants of thechallenge-and-response. In this paper, we propose a novel means to constructthe above mechanism by use of unidirectional communication instead ofbidirectional communication. Our proposal is based on the assumption that amobile terminal incorporates a high-precision inner clock in a tamper-resistantprotected area. In positioning, the mobile terminal uses its inner clock andthe time and location information broadcasted by radio from trusted stations.Our proposal has a major advantage in protecting the location privacy of mobileterminal users, because the mobile terminal need not provide any information tothe trusted stations through positioning procedures. Besides, our proposal isfree from the positioning error due to claimant's processing-time fluctuationsin the challenge-and-response, and is well-suited for mobile terminals in theopen air, or on the move at high speed, in terms of practical usage. We analyzethe security, the functionality, and the feasibility of our proposal incomparison to previous proposals.
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