Research On Chaos Based Encryption Algorithm And Hash Function Construction

With the rapid development and extensive applications of computer and communication technologies, our society goes into information time. The establishment of information system has gradually become an essential foundation for nearly all fields of our society. However, since the sharing and the openness of the network, the security of multimedia information has been threatened. The cryptography, which aims at the security of information, has become one of the important research fields in information science and technology.Due to the chaotic system with like-random, high sensitivity to initial value and unforeseeable properties, it has become current research hot spot. Many literatures indicated that encryption algorithm based on a single chaotic system may result in low security, easy to be broken. Then, new encryption systems are urgently needed. In this dissertation, chaos-based encryption algorithm and Hash function have been carefully studied. And can try to applied them to protect the security of information.The following tasks have been accomplished in this dissertation:In this article, briefly introduce the background and significance of the chaotic encryption. Moreover, the research status of chaotic stream ciphers and Hash functions have been summarized.In the second chapter, giving a brief introduction to the three definitions of chaos and its basic characteristics and decision methods. And describe some common chaotic models. Then introduce cryptography and cryptanalysis theoretical knowledges.In the third chapter, a composite chaotic dynamical system is investigated based on the coupled Logistic map and the piecewise linear chaotic map. And a stream cipher algorithm is designed based on the composite chaotic dynamical system. In this paper, we have simulation and security analysis. The security analysis indicated that this algorithm is effective, key and plaintext and ciphertext form complex and sensitive nonlinear relations, and the correlation is very small. The leaking of ciphertext to key and plaintext information can be effectively prevented.In the fourth chapter, an algorithm for one-way hash function construction based on composite chaotic dynamical system is investigated in this paper. In order to achieve high security in hash function, we are combining a piecewise linear chaotic map and a coupled Logistic map. The segmentation parameter of piecewise linear chaotic map is produced by the coupled Logistic map. Then, the final hash value is obtained by means of the linear transform on the iteration sequence. Theoretical analysis and computer simulation indicate that the Hash function which we constructed with good statistical properties and collision-avoided. And the proposed algorithm can satisfy the performance requirements of Hash functions.Finally, the research work of this dissertation is summarized, and the future developing direction is indicated.