Research On Physical Layer Security Protocol In Wireless Network

Due to the broadcast nature of wireless channel, wireless communication is prone to being attacked, many attacking methods, such as eavesdropping, message modification, and node impersonation, are presented. Thus, wireless security causes much attention. On one hand, more and more computing resources can be obtained by the attacker, on the other hand, the energy and computational resources of wireless devices is limited, computational-security-based Cryptosystems restricted the further development of wireless networks. Hence, as an ingenious solution, the physical-layer-security-based approach with low power, low computational complexity and high security becomes one of the hot research topics in wireless security.In this dissertation, physical-layer-based key distribution and message authentication are the main thought. To overcome the limitations of existing physical layer-based key generation schemes, such as low key generation rate, low key entropy, and high reliance on mobile environments, two new physical layer approaches are proposed. Both of them provide a guarantee for fast and secure key distribution in wireless communication. Owing to the low authentication rate and low security of the existing message authentication protocols over noiseless channel, a new authentication framework over noise channel is presented. Under this framework, an efficient messages authentication protocol with high security is proposed. The framework and protocol above fill a gap in physical-layer-based authentication, and provide a theoretical basis and guidance for message authentication in wireless networks. The main contents and contributions of this dissertation are listed as follows:Fristly, to improve the performance of the physical-layer-based key generation schemes, including the generation rate, the key entropy and the reliance on mobile environments, a new artificial-interference-based key extraction scheme named SmokeGrenade is established. SmokeGrenade changes the measure values on channel states information through leveraging the artificial interference from a collaborative node, and utilizes the information exchange between collaborative node and one of the keying nodes over a secure channel to maintain the measurement correlation between the keying nodes. The proposed approach provides high key generation rate and entropy, and can be applied in static environment. Theoretical analysis proves that the achievable key generation rate of SmokeGrenade gains three times better than those of the traditional schemes while the average interference power is normalized to 1. Simulation results also shows that SmokeGrenade achieves a higher generation rate, higher key entropy and lower reliance on mobile environments compared with some state-of-the-art approaches.Secondly, to improve the efficiency of bit extraction and artificial jamming on SmokeGrenade, a new protocol named SKEAN, which based on interference-reuse and adaptive multi-bit extraction, is proposed. SKEAN leverages the strategy of artificial interference-reuse, in which the collaborative node keeps sending the jamming signals in each coherence time, to increase the measured value of keying nodes. Then SKEAN utilizes low entropy measurements elimination and random permutation to eliminate the low entropy measurements and break the correlation between the adjacent measurements, respectively. Finally, SKEAN uses adaptive multiple-bit extraction to improve the bit rate. The theoretical result shows that our scheme can make hundred times better than the existing approaches when the coherence time equals to 200 ms. Simulation results also show that SKEAN has higher generation rate, key entropy and reliability compared with the state-of-the-art schemes.Thirdly, for the lack of authentication framework over noise channel, a new authentication framework over wiretap channel model is proposed. Traditional authentication framework is based on a noiseless channel. Besides a noiseless channel between legitimate users which is full controlled by the adversary, a noise channel is also included in this framework. Thus, it can be seemed as an extension of traditional framework. The framework assumes that a secret key is shared by legitimates. Its basic ideal is that: the sender encodes the message to the codeword which includes two parts, and then sends one part over the noiseless channel and transmits the other part over the noise channel; once those two parts are both received, the receiver authenticate and recover the message with the secret key. This framework also defines the efficiency measure of an authentication protocol formally.Finally, to address the problem of the low efficiency of the existing physical-layer-based authentication protocols, a new message authentication protocol under the above framework is presented. In this protocol, Alice firstly generates a tag with message and key; then encodes the tag to a codeword by using random coding technique; and then, sends the message over noiseless channel and transmits the codeword over wiretap channel. Through detailed analysis of adversary model and rigorous mathematical derivation, it is concluded that under information theoretic security the scheme can realize polynomial times authentication with the same secret key. Furthermore, the theoretical result also proves that the channel coding rate is larger than the secrecy capacity of the wiretap channel when the tag rate is fixed.