Cooperative Secret Key Exchange Based On The Physical Layer For Ad Hoc Network

Ad Hoc network is a special wireless network with the properties of multi-hop,decentralization and self-organization.It applies to the environments that are subject to poor communication environment and lack infrastructures.Now,Ad Hoc network has become one of the key technologies in 5G,since it can be built conveniently without fixed infrastructures.However,Ad Hoc network faces many security challenges due to the wireless channels and the mobile terminals.In order to ensure communication security,5G white paper suggests that the communication content should be encrypted end to end.Here,secret keys must be generated and shared between two terminals before secure communication.How to securely distribute secret keys is essential to this kind of networks.In terms of key agreement,many schemes have been proposed by academia and industry in the past ten years.The physical layer key generation method is suitable for Ad Hoc network,for it can be used to generate secret keys without complex protocols and key distribution center.Our main work of this paper is described as follows:(1)After studying the existing schemes,we find there are several problems including the low key generation rate and the high rate of the bit error rate in the basic key generation schemes.In addition,we analyze the strong hypothesis of the relay node in the scheme with the relay node.We discuss some important technologies about phase estimation,quantization,key reconciliation and privacy amplification.(2)To solve the problems in the existing schemes,based on the schemes with a relay node,we propose a scheme with “virtual relay”.The scheme removes the strong assumption that the relay node must be a trusted one.Firstly,two terminals respectively choose two bit strings from their secret key pool.Next,with the basic physical layer secret key generation scheme,they combine the selected bit strings to generate a string as secret key.The experimental results show that the scheme can generate secure secret key with good randomness in high rate.(3)In order to solve the secret key generation problem within two hops,we propose a cooperative secret key generation scheme with two non-collusion relay nodes.In this scheme,bit strings from relay nodes are mixed,which can blind the original information.It ensures that neither the eavesdropper nor the relay nodes can get the secret key information.In addition,a novel protocol is proposed to determine that the relay nodes don’t transmit error bit strings to terminals.Here,it’s not necessary to assume that the relay nodes must be trusted nodes.The simulation results show that our scheme can generate the secret key in two hop network with information-theoretical security.