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Study On Chaos-based Cryptography And Its Application In Secure E-mail System

Posted on:2007-03-15Degree:DoctorType:Dissertation
Country:ChinaCandidate:F PengFull Text:PDF
GTID:1118360272466025Subject:Circuits and Systems
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The broad relations between the chaos theory and the conventional cryptography have aroused interest of more and more researchers, and using chaotic system to construct cryptography algorithms becomes an important research hotspot in information security field. Generally, there are two kinds of chaotic communications. One is of chaotic secure communications for wireless application (most of them are based on chaos synchronization techniques), the other is digital chaotic cipher for Internet application. As for the first kind of communication systems, at present, their applications are restricted by their inability of tolerance on the noise. On the other hand, the digital chaotic cipher, which analog to the conventional cryptography, seems to be extended to all fields of cryptography, such as symmetric key cryptography, public key cryptography (asymmetric key cryptography), one-way hash function, digital signature, and so on. For this reason, the content in this dissertation are mainly on digital chaotic cipher except for some special comment.From about 1990 to 2000, chaos-based ciphers were developed, and symmetric key cryptography was the main research target. Many ciphers presented were analyzed and attacked. At the same time, there were some methods proposed to design and analysis of digital chaos-based ciphers, which provide good references for researchers.After 2000, the research of the chaos-based cipher is extended to asymmetric cipher, one-way hash function and some other fields of conventional cryptography, this means that the chaotic cipher has developed to a new stage.Our contributions in this dissertation involve the following aspects: review and analysis on chaos-based public key cryptography, research on chaos-based image encryption algorithm with external keys, research on chaos-based block cipher, research on one-way hash function based on iterated chaotic systems and digital signature based on chaotic systems and elliptic curves. In the last chapter, we propose a secure E-mail system that uses chaos-based cryptography.The main contributions contained in this dissertation include:1. An overall introduction of three new chaos-based public key cryptography algorithms is given in this dissertation. They include: RSA-like and ElGamal-like public key cryptography based on Chebeshev chaotic map, public key cryptography based on DDE and public key cryptography based on GSCML. Based on the introduction of the three algorithms, we have the analysis of them and the discussion of possibility of their applications.2. For the advantages of the characteristics of chaotic systems, the research on chaos-based image encryption/decryption is becoming an important application filed of chaos-based cryptography. Usually, a chaotic cipher uses system parameters or initial values or both of them as the secret key, so the storage and transformation of the secret chaotic key are inconvenient and the design of key space is also a problem. We propose a chaos-based image encryption/decryption algorithm with external keys, and two different methods are presented by using a single chaotic system and mixed chaotic systems, respectively. Analysis shows that they have good security and can resist many kinds of attacks.3. A novel block cipher based on chaotic systems is presented. It needs not discretize the chaotic maps, but uses long binary fractions and some other transformations to avoid float operations. At the same time, according to Shannon's theory, diffusion and confusion are used in the algorithm for improving the security of the cipher. Simulation and analysis show that the new block cipher has a good performance.4. A general model of one-way hash function based on iterated chaotic systems is constructed. The general construction method of this kind of one-way hash function is studied and classified, and the analysis methods for their security are also described. Based on the general model, we construct two one-way hash functions based on iterated chaotic systems, and their performance and security are also evaluated.5. A digital signature based on chaotic systems and elliptic curves is presented, in which chaos-based cipher is used to strength the security of ECDSA. Compared to ECDSA, the proposed algorithm can resist single message leak-out attack, repeat use of single message key attack and repeat use of signature key attack.6. By use of the above-mentioned results of research on chaos-based block cipher, one-way hash function based on iterated chaotic systems and digital signature based on chaotic systems and elliptic curves, we propose a secure E-mail system. The application and analysis show that chaos-based cipher can fulfill the requirements of the real application.
Keywords/Search Tags:chaotic system, chaos-based cryptography, cryptography, block cipher, image encryption/decryption, one-way hash function, digital signature, ECDSA, secure E-mail system
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