Round-Trip Delay Consistency Measurement Based Key Agreement for Remote Wired Multi-Hop Networks
Qi Xuehao1,2, Liu Xiyu1, Song Yubo1,2,3, Tang Xusheng1,2, Yao Qigui4
1. School of Cyber Science and Engineering, Southeast University Nanjing 210096 China; 2. Purple Mountain Laboratories Nanjing 210096 China; 3.Xinjiang Production & Construction Corps Key Laboratory of Green and Intelligent Development and Efficient Utilization of Strategic Mineral Resources School of Big Data and Information Engineering Xinjiang University of Technology Hotan 848000 China; 4. China Electric Power Research Institute Co. Ltd Nanjing 210003 China
Abstract：Conventional key agreement schemes rely on computational hardness assumptions and are vulnerable to future quantum attacks, while wireless physical-layer methods based on channel reciprocity suffer from distance sensitivity and poor adaptability to multi-hop topologies. To address these issues, this paper proposes a remote key agreement mechanism for wired multi-hop networks that exploits the consistency of network-layer round-trip time (RTT) as a candidate entropy source. The legitimate endpoints perform active probing using Internet Control Message Protocol (ICMP) Echo requests and replies, record bidirectional RTT sequences, and extract frequency-domain magnitude spectra of delay jitter to characterize the path response. After weighted moving average (WMA) preprocessing, cumulative distribution function (CDF)-based quantization generates initial bit sequences, followed by Cascade information reconciliation and 2?universal hashing privacy amplification to produce a final consistent key. Experiments on a cross-regional cloud testbed show that the average initial key agreement rate reaches 72.33%, and after reconciliation the final consistency is 100%. The generated keys pass the National Institute of Standards and Technology (NIST) randomness tests, with an average generation rate of about 500?bit/s. Furthermore, path-internal eavesdropping experiments demonstrate that an adversary observing only local link delays achieves bit agreement rates close to random guessing (≤54.4%), confirming the structural asymmetry of bidirectional RTT measurements. A quantitative information-theoretic analysis shows that the scheme can extract about 834 bits of secure key under typical parameters. This work extends the entropy source of unconditionally secure key generation from physical-layer wireless features to network-layer delay characteristics, offering a practical solution for remote terminal key establishment in power communication networks and similar infrastructure scenarios without relying on public-key infrastructure.
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