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Title: Secret Key Agreement over Two-Way Broadcast Channels
Authors: Ahmadi, Hadi
Safavi-Naini, Rei
Keywords: Theoretic security, broadcast channels
Issue Date: 19-Nov-2009
Abstract: Wyner, and later Csisz´ar-and-K¨orner, studied the problem of secure communication over noisy channels. They proved that positive rates for one-way secure communication are achievable provided that the eavesdropper’s channel is noisier than the main channel. This paper considers the problem of information-theoretically secure key agreement when Alice and Bob are connected by a two-way noisy broadcast channel: that is, each party has access to a noisy broadcast channel that they can use for sending messages. We define secrecy capacity (for key agreement) of twoway broadcast channels and obtain a lower bound by presenting three key agreement protocols. In the first two protocols the key is effectively determined by one of the parties and securely delivered over the noisy channels. The third protocol, however, uses a novel interactive channel coding technique that results in a shared key which is a noisy version of the initiator’s message. We apply our results to the case that the noisy channels are binary symmetric and derive expressions for the secrecy capacities of the three protocols. We show that by using interactive coding, in some cases, it is possible to establish a secure key even if the main channel is 10 times noisier than the eavesdropper’s channels. Our results have theoretical and practical significance. We discuss our results and future work.
Appears in Collections:Safavi-Naini, Rei

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