Key Evolution And Encryption Over Wireless Channels

Physical-layer channel noise can be used to enhance the security performance of the system in wireless networks. In general, a physical-layer security protocol is tailored to the channels and relies on the assumption that knowledge on the eavesdropper’s channel is available. However, this assumption is not practical.In this paper, we focus on the problem of developing key agreement schemes for secure communication across wireless channels, and propose a key evolution scheme and design an encryption mechanism based on dynamic secrets. The basic idea of key evolution is that, key evolution allows the legitimate users’ keys to evolve continuously based on the transmitted messages over the noisy wireless channel without assuming that the channel characteristics of the enemy are known. Even if the eavesdropper’s channel is superior in some scenarios, the legitimate parties can establish secret keys, provided that the channel is authenticated. Key evolution is an increasing process of entropy in the information theory. Comparing with common user name and password authentication technology, the existing security system will be leaked and more likely to be attacked, while the key in key evolution gets more and more secure as time goes on.We begin by discussing a special wiretap channel with a noiseless main channel and a binary symmetric channel(BSC) as the wiretapper’s channel, then extend it to a more generalized wiretap channel that have BSCs as both the main and wiretapper’s channel. We construct a key evolution protocol based on dynamic secrets and make an analysis of the security features of the agreement. Finally, we propose a novel k-resistance encryption scheme(k-RES) that can use different keys to encrypt and decrypt messages if there are no more than k bits differ between the encryption and decryption keys. The objective of k-RES is to utilize the slightly different keys to encrypt a relatively small size message. If a pair of keys only has no more than k-bit different, the receiver can recover the message; otherwise he should get no information about the message. We show that this scheme can be viewed as a conceptual wiretap channel that has a main channel with error probability no more than k/n and a worse wiretap channel. Using the threshold properties of some codes, we can design k-RES to achieve secure and reliablecommunication.