Research On Applications Of Chaos Cryptography To Wireless Sensor Networks Security

For its large application value, wireless sensor networks (WSN) have attracted military, industrial and academic attention all over the world since 1990s'. However, the application environment, topology and characteristics of WSN node make WSN vulnerable to security threaten. Consequently, the security problem becomes the decisive factor for WSN's practical application. Choosing suitable cryptographic and authentication algorithm is the key to WSN security problem. But the unique characteristics of WSN node, such as pool computing ability, small memory and little power, result in a fact that there is little cryptography suitable to WSN. Therefore, it is necessary to do more detailed research on new cryptography and authentication for WSN.As a very complicated phenomenon of nonlinear system, chaos have inherent cryptographic properties such as sensitive to parameter and initial state. Since 1980s', chaotic cryptography has gained greatly improvement. Therefore, It provides a novel approach to WSN encryption and authentication.For the application of chaotic cryptography to solve WSN security problem, the following contributions have been accomplished and are as follows:In order to prove the feasibility of the application of chaos to WSN, first, WSN structure and security problem have been introduced. By analyzing a few classic cryptographic schemes, we find that it is necessary to design the new cryptography suitable for WSN. Second, based on the discussion about relationship between chaos and cryptography, we prove that it is feasible to apply chaos to WSN.In order to prove that chaotic block cipher is more suitable to WSN, the relationship between chaotic cryptography and traditional cryptography have been discussed first. Although chaos have inherent cryptographic property, the basic principles must be obeyed. Second, by discussing about characteristics of chaotic stream cipher and chaotic block cipher, we prove that chaotic block cipher is more suitable for WSN.In order to verify the opinion about obeying basic principles, typical chaotic stream cipher and chaotic block cipher have been analyzed in detail. First, chaotic stream model has been studied, and chaotic stream analyzing methods have been concluded. Based on the detailed analysis of two chaotic stream ciphers, we find their design flaws, and then use the chosen plaintext attack to recover their keystream successfully. Second, a chaotic block cryptosystem based on Feistel (WSN cryptosystem) is introduced. By means of differential cryptanalysis to WSN cryptosystem, we recover the key from 3 turns and 4 turns successfully. The above facts verify the opinion about obeying basic design principles.In order to finish the encryption and authentication in WSN, a chaotic block cryptosystem based on Feistel, which combines cryptographic and hashing scheme (WSNHC), is proposed. First, since Feistel-type block ciphers have some inherent advantages, we prove that the chaotic block cryptosystems based on Feistel are more secure. Second, according to the design principles of Feistel-based block cipher, we analyze all the drawbacks of WSN cryptosystem in detail. Third, in order to fulfill authentication, the other requirement of WSN security, we improve the original WSN cryptosystem to a combined chaotic cryptographic and hashing cryptosystem (WSNHC). Since WSN characteristics are considered and the basic principles about Feistel-type block cipher are also obeyed, the encryption algorithm of WSNHC can both suit WSN and have higher security property. In addition, the hash function of WSNHC generates hash value during encryption process, which brings WSNHC higher efficiency. Simulation of WSNHC verifies its performances of encryption and hash.In order to solve the secure routing problem of WSN, a new secure routing algorithm (WSNSR) based on WSNHC is proposed. First, the contradictions between traditional wireless routing algorithm and WSN environment have been analyzed. We use WSNHC and some corresponding mechanisms to solve the problems including routing information exposure, routing information falsification and DoS attacks. Second, by combining the table-driving routing algorithms and demand routing algorithm, we propose some approaches to guarantee the routing reliability and efficiency, including random gaining routing information, middle node replying RREQ and optimized route selecting. Theoretical analyses show that WSNSR has higher security property and routing efficiency.Finally, the research work of this dissertation is summarized, and the future developing direction is indicated.