Design And Implementation Of PC Storage Encrypting System Based On Chaos

Along with the fast development of the information technology, computer has come to pervadeevery aspect of our lives and work, and various information security problems that follows it arebecoming more and more prominent and could not be neglected. Accidental divulge, illegal stealingand misrepresentations of the confidential documents are one of the common hidden dangers, andhow to solve this kind of problem is always in the face of people. Cryptographic technology is thecornerstone to solve information security problem, and data encryption technology is one of themost effective method to prevent this kind of hidden danger. Chaos has established closerelationship with traditional cryptography because of its natural excellent characteristics, such as,initial value sensitivity, periodicity as well as randomness, and gradually formed a new subject—chaotic cryptography. In this article, chaos were combined with stream cipher and block cipher, onthis basis, an encrypting file system based on chaotic stream and chaotic block cipher had beendesigned and achieved under VC++ platform. It was appropriate to encrypt kinds of files in PC, atthe same time, it was also can be used to encrypt files in mobile storage which was connected withPC. The main work is as follows:(1)The basic knowledge of chaos and cryptography, distinction and relation between those twowere introduced, including the basic concept of chaos, stream cipher and block cipher, theencryption principle of DES and Triple DES which were used in the proposed encrypting filesystem. On this basis, the ways of the selection of chaos map and the design of the chaoticcryptography were elaborated in detail. This theory work laid a foundation for the consequentresearch in practice.(2)A new chaotic system based on Rossler function was put forward, and its dynamicalbehavior was further investigated, including: symmetry, the balance point, stability, Lyapunovexponent’s spectrum, and bifurcation. The method of the implementation of chaotic system and thegeneration of the chaotic PN (Pseudo Noise) sequence based upon DSP was described. At last, asoftware package STS which was used to test the sequence performance was introduced, includingits 15 test indexes and the judging standard of the test results. The software package was publishedby NIST (National Institute of Standards and Technology). The sequence performance’s test resultsof the new chaotic system was given as followed, and it showed that the sequence performance wasgood enough to meet the need of the secure communication system.(3)A chaotic encrypting system was designed and implemented under VC++ platform. Thepassword to log in the system was stored in database as its hash value, not in plain text, which make the storage of the password safer. System included three cryptographic algorithms: chaotic streamcipher, chaotic block cipher based on DES and chaotic block cipher based on Triple DES. ChaoticPN sequence was used as the key stream in chaotic stream cipher, and in the other two algorithms, itwas used as the seed key. The algorithms used the chaotic binary sequences as the key to encryptfiles, such as documents, pictures, audio-videos and so on. Chaotic stream cipher was the mostcommon algorithm in chaotic cryptography. In order to overcome the problem of the key spaceshortage of DES, the one-group-one-cipher was used to combine the chaos and DES, and expandingkey space was reached., one-group-one-cipher means every block has the different key. In case ofplaintext space shortage,chaotic block cipher based on Triple DES can remedy the defect thatchaotic DES block cipher cannot resist exhaustive attack in each group.(4)The performance of the encrypting file system was analyzed. The file system has threedifferent chaotic systems, including discrete chaotic system, continuous chaotic system, andcontinuous hyper chaos system. Based on the analysis methods of block cipher and stream cipher,the key space, key sensitivity and sequence performance of the three chaotic systems was analyzedto evaluate the security of the encrypting file system. The three different classes chaotic systems’key space respectively reach 1029, 7.5×1042, 2.8×1071, which showed that they can resistedexhaustive attack perfectly in the current computer speed. The result of the key sensitivity testshowed that the accuracy degree of the key reached 1/100000. In the encrypting speed test, thespeed of the chaotic stream cipher reached 200M per minute, was the fastest speed in the threealgorithm,。Because of the algorithm complexity, the other two algorithms were inferior to thechaotic stream cipher, but the speed can meet encryption demand. The system has some propertiessuch as high security, convenient operation and friendly interface.