A new secure multi-hop untrusted relaying scheme
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Cooperative relaying is utilized as an efficient method for data communication in wireless sensor networks and Internet of Things (IoT). However, sometimes due to the necessity of multi-hop relaying in such communication networks, it is challenging to guarantee the secrecy of cooperative transmissions when the relays may themselves be eavesdroppers, i.e., we may face with the untrusted relaying scenario where the relays are both necessary helpers and potential eavesdroppers. To obviate this issue, a new cooperative jamming scheme is proposed in this paper, in which the data can be confidentially communicated from the source to the destination through multi-hop untrusted relays. Toward this end, we first consider a two successive untrusted relaying network, i.e, a three-hop communication network. In our proposed secure transmission scheme, all the legitimate nodes contribute to provide secure communication by smartly injecting artificial noises to the network in different communication phases. Given this system model, a novel closed-form expression is presented in the high signal-to-noise ratio (SNR) regime for the ergodic secrecy rate (ESR). Furthermore, we evaluate the high SNR slope and power offset of the ESR to gain a basic comparison of the proposed secure transmission scheme and the state-of-arts. Our numerical results highlight that the proposed secure transmission scheme provides better secrecy rate compared with the two-hop untrusted relaying scheme as well as the direct transmission scheme.
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