Junwei Zhou

An Efficient File Hierarchy Attribute-Based Encryption Scheme in Cloud Computing

Ciphertext-policy attribute-based encryption (CP-ABE) has been a preferred encryption technology to solve the challenging problem of secure data sharing in cloud computing. The shared data files generally have the characteristic of multilevel hierarchy, particularly in the area of healthcare and the military. However, the hierarchy structure of shared files has not been explored in CP-ABE. In this paper, an efficient file hierarchy attribute-based encryption scheme is proposed in cloud computing. The layered access structures are integrated into a single access structure, and then, the hierarchical files are encrypted with the integrated access structure. The ciphertext components related to attributes could be shared by the files. Therefore, both ciphertext storage and time cost of encryption are saved. Moreover, the proposed scheme is proved to be secure under the standard assumption. Experimental simulation shows that the proposed scheme is highly efficient in terms of encryption and decryption. With the number of the files increasing, the advantages of our scheme become more and more conspicuous.

A Modified Chaos-Based Joint Compression and Encryption Scheme

An approach for improving the compression performance of an existing chaos-based joint compression and encryption scheme is proposed. The lookup table used for encryption is dynamically updated in the searching process. Once a partition not matched with the target symbol is visited, this and other partitions mapped to the same symbol are reallocated to a nonvisited symbol. Therefore, the target symbol eventually associates with more partitions and fewer number of iterations are needed to find it. As a result, expansion of the ciphertext is avoided, and the compression ratio is improved. Simulation results show that the proposed modification leads to a better compression performance, whereas the execution efficiency is comparable. The security of the modified scheme is also analyzed in detail.

Chaos-based joint compression and encryption algorithm for generating variable length ciphertext

Here we modify a chaos-based joint compression and encryption algorithm previously proposed by us. Two modifications are suggested for improving the compression performance and generating ciphertext with variable length, respectively. The first goal is achieved by counting the number of distinct symbols visited by the chaotic search orbit, rather than the total number of iterations of the chaotic map. The second objective is realized by introducing a user-chosen parameter to determine the ratio between the search and the mask modes. The performance of the modified algorithm is justified by simulation results using standard test files.

A block chaotic image encryption scheme based on self-adaptive modelling

In this paper, we suggest a block image encryption algorithm which can give us an efficient scheme to hide and encrypt image data. Only the diffusion function, instead of classical permutation plus diffusion operations, is adopted. The plain-image is firstly divided into two equal parts randomly by vertical, horizontal, or diagonal directions. Then encryption of one part depends on the other part, in which the keystream is generated by the plain-image, i.e., one of the two parts. An error concept is added in the initial conditions in every round. It means that the keystreams are different in the process of encryption steps. The error may be positive or negative decided by a rule of sign function. Experiment results show that the proposed method can provide a high security of cryptosystem, and can reduce the computation redundancy compared with that of the traditional architectures such as Arnold map based method, and totally shuffling based method.

Wave atom transform based image hashing using distributed source coding

To reduce the size of hash code and enhance the security of wave atom transform (WAT) based image authentication system, a low-density parity-check code based distributed source coding (DSC) is employed to compress the hash code. With the help of a legitimately modified image, the compressed hash value could be correctly decoded while it will fail with the help of a maliciously attacked image. Therefore, the employed DSC provides a desired robustness to image authentication. Simulation results indicate that the proposed scheme provides a better performance with less hash code than existing WAT based image hash without using DSC. Moreover, the proposed scheme outperforms the random projection based approach in terms of authentication accuracy and data size.

Distributed Block Arithmetic Coding for Equiprobable Sources

Distributed arithmetic coding (DAC) is similar to syndrome coding, in the sense that message sequences sharing the same interval can be considered a coset of the space of the source sequences, and the codeword is the index of the coset. In this paper, the minimum Hamming distance of cosets is studied and it is proved that such a distance is as small as one. By only allowing the sequences with a large Hamming distance to overlap in the same interval, an improved DAC scheme is proposed. Simulation results show that, for equiprobable memoryless sources, this approach outperforms DAC in terms of decoding error rate at the same coding cost. In addition, at small sequence length, the decoding error rate of the proposed scheme is lower than that of distributed source coding based on low-density parity-check codes for highly correlated sources.

Distributed arithmetic coding with interval swapping

In distributed source coding, ambiguity is usually introduced in the encoding process as it allows multiple plaintext sequences encoded to the same codeword. All these plaintext sequences are decodable and are considered as candidates at the decoder. With the help of side information, the decoder is able to determine which sequence in the candidate set is the best choice. Both the cardinality and the minimum Hamming distance of the candidate set are significant to the decoding performance. In this paper, a Slepian-Wolf code based on arithmetic coding is studied. By employing the interval swapping technique, a linear code is incorporated into binary arithmetic coding. The incorporated linear code improves the minimum Hamming distance within the candidate set which leads to a lower bit error probability. Moreover, binary arithmetic coding exploits the a priori knowledge of the source to reduce the cardinality of the candidate set. Simulation results show that this approach leads to superior performance for moderately skewed sources with linear encoding complexity, which meets the low power consumption requirement of applications such as wireless sensor networks and low-complexity multimedia compression. HighlightsBy imbedding a linear code in binary arithmetic coding, a Slepian-Wolf code is proposed.The linear code improves the minimum Hamming distance within the candidate set.The binary arithmetic coding reduces the cardinality of the candidate set.Simulation results show that this approach leads to superior performance.

Enhanced Cryptography by Multiple Chaotic Dynamics

A potential security vulnerability of embedding compression in a chaos-based cryptography is studied. Furthermore, a scheme for improving its security is proposed. This correspondence considers the use of multiple chaotic dynamics and drive chaotic trajectory by both plaintext sequence and initial values of a chaotic map. Chaotic trajectory is used for encryption that is never reused for different plaintext. This makes that scheme naturally resist chosen plaintext attack and cipher text-only attack. Its strong security is justified by the key space, key sensitivity, and tests of random number sequences. The results show that the security of the proposed scheme is stronger than the latest algorithm especially in resisting chosen plaintext attack, while its performance is not sacrificed.

Image authentication using distributed arithmetic coding

Image authentication using distributed arithmetic coding (DAC) is studied in this paper. The quantized random projections of the original image are compressed by a DAC encoder and the codeword is taken as the authentication data. With the help of a target image as side information, the DAC decoder could recover the projections. The authentication process is achieved by examining the Euclidean distance between the reconstructed projections and the side information. Compared with existing approaches, the proposed approach has a simpler structure without the help of an additional cryptographic hash function to verify the decoding result. Moreover, the authentication data is more compact with fewer size. Simulation results justify that the proposed approach achieves a comparable performance as existing schemes.

Wave Atoms Based Image Authentication Using Slepian-Wolf Coding

To reduce the size of hash code and enhance the security of wave atoms based image authentication system, a Slepian-Wolf (SW) code is employed to encode the hash code. With the help of a legitimately modified image, the compressed hash code could be correctly decoded while the decoding will be failed with the help of a maliciously attacked image. Therefore, the SW code could provide a desired robustness to image authentication. Simulation results indicate that the proposed scheme provides a better performance with less hash code than the existed approach. Moreover, the proposed scheme outperforms the random projection based approach in terms of authentication accuracy and data size.