Research On Mechanism And Application Of Ternary Key Stream Generator

With the development of computer and communication technologies, information hasbeen considered as an important strategic resource, and the capability of protectinginformation security has become an important part of a country's comprehensive nationalstrength. Information encryption is the key technology and important method of protectinginformation security at present, which plays an important role in the politics, military,business, finance and other applications. Many countries around the world have developedtheir own encryption systems, and China has also put the development of new state-ownedcryptography as a priority research project in the information field. Symmetric cryptographyhas been widely used in various fields because of its fast and convenient advantages, and oneof the key issues in symmetric cryptography is the design of the key stream generator.The main research work in this paper includes two aspects:1. Propose a ternary key stream generator based on discrete trajectory transform ingeneralized information domain.Generalized information domain (GID) is the space of all digital information that can beexpressed by binary code. The ternary key stream generator introduces GID as the space ofentropy source and the generalized information that user chooses as true random entropysource. Since user's choice is random and arbitrary, it's necessary to eliminate the statisticaldefects existing in the entropy source. We design a multi-round reconstruction method topretreat the entropy source, and use multiple crucial technologies to obtain a backgroundwhich satisfies the requirements of size and statistical properties. On this basis, we employ aninitial random dynamic element which is time-varying, random and personal, and use somemethods such as space mapping, constraint judgment and periodic orbit-changed control torealize the discrete trajectory transform on the background by iteration-feedback mechanismand generate a key stream of any length which has good properties.The ternary key stream generator takes the initial random dynamic element as the initialvalue, and the generalized information, reconstruction parameters, trajectory transformparameters as the key space, which form the ternary structure together with the key streamgeneration algorithm. The ternary key stream generator has a large key space, passes the strictrandomness test NIST SP800-22, and shows good chaotic properties such as sensitivity toinitial value and avoidance of repeated period. The ternary key stream generator constructs adiscrete chaotic dynamical system with true random entropy source user chooses and is ableto provide no-repeat key streams for a long time. 2. Based on the characteristics of the ternary key stream generator, we study itsapplication in cryptography and propose a ternary dynamic encryption algorithm.The ternary dynamic encryption algorithm consists of three parts: dynamic blockencryption, trajectory address permutation and stream encryption. In dynamic blockencryption, the plaintext is expanded and devided to groups, and the bytes at the symmetricaddresses are transformed to finish the confusion and diffusion process in each group. Thenwe use the trajectory address permutation and stream encryption to finish the overallpermutation and confusion process. The ternary dynamic cryptographic algorithm showssatisfactory encryption and decryption performances. It is able to well hide the statisticalcharacters of plaintext such as histogram, entropy value and distribution of neighboring pixels;moreover, it shows good sensitivity to initial value. In the ternary dynamic encryptionalgorithm, the length of ciphertext and the details of encryption algorithm are dynamicallydetermined by the key stream and trajectory address sequence, which hides the length ofplaintext and realizes the changeability of the encryption algorithm. With chaotic properties ofthe ternary key stream generator, the ternary dynamic encryption algorithm technicallyensures that the generated key streams and encryption algorithms do not repeat, which helpsto achieve the result of "One time ciphertext". In practical use, the key space is encapsulatedfor users and do not need transmission through secure information channels, while the initialvalue can be transmitted together with the ciphertext through public information channels.The ternary key stream generator and the ternary dynamic encryption algorithm based ondiscrete trajectory transform in generalized information domain are independently proposedby our research team. The idea and implementation method of this cryptosystem are bothinnovative. The cryptosystem has passed the national secure test and been authorized fournational invention patents; moreover, several cryptographic products are developed based onit. The cryptosystem proposed in this paper is quite suitable for guaranteeing informationsecurity in some important fields such as national defense.