The 2018 International Symposium on Information Theory and Its Applications (ISITA2018)


Session Number:We-PM-1-4



The Symmetric Two-Hop Channel with an Untrusted Relay

Shahab Ghasemi-Goojani,  Panagiotis Papadimitratos,  


Publication Date:2018/10/18

Online ISSN:2188-5079


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We study, using information-theoretic security methods, the so-called symmetric two-hop channel with an untrusted relay. In this model, a source wants to send its message reliably and securely to the destination through an honest but curious relay. The relay acts as a passive eavesdropper. Our investigation, in line with the relevant literature, seeks to determine what rate, termed secrecy rate, is achievable. To do that, we consider a typical setting, with the destination cooperating with the source, sending a ’scrambling’ signal to conceal the message from the relay. To derive the achievable secrecy rate, we propose a novel scheme based on nested lattice codes. We show that our scheme outperforms all existing schemes and it achieves the outer bound for this channel model within 0.33 bits.