An Algebraic Quality-Time-Advantage-Based Key Establishment Protocol

The essence of information assurance resides in the ability to establish secret keys between the legitimate communicating parties. Common approaches to key establishment include public-key infrastructure, key-distribution centers, physical-layer security or key extraction from common randomness. Of these, the latter two are based on specific natural advantages that the legitimate parties hold over their adversaries -- most often, such advantages rely on superior or privileged communication channels. This paper tackles a key-establishment protocol that relies on a completely different type of advantage: time. The protocol builds on the idea that when two devices are able to spend a pre-determined, mostly uninterrupted, interval of time in the company of each other, and when such a feat is outside the capability of any realistic attacker, then the legitimate parties should be able to establish a secret key without any prior common information. The paper presents a basic efficient time-based key establishment protocol, and demonstrates how it can be extended to follow customized information transfer functions and deal with predictable fluctuations of wireless interference.