A Spectrum-Efficient Cross-Layer RF Distance Bounding Scheme

Figure 3

A typical distance bounding protocol consists of a setup phase, an exchange phase, and a verification phase. In the most critical exchange phase, the verifier estimates the distance bound by timing the round trip time of cryptographic challenge and response bits. To enhance the protocol security against physical layer attacks, most cross-layer distance bounding schemes focus on effectively minimizing and measuring the RTT.