Xu Zhengquan

Digital chaotic sequence generator based on coupled chaotic systems

Chaotic systems perform well as a new rich source of cryptography and pseudo-random coding. Unfortunately their digital dynamical properties would degrade due to the finite computing precision. Proposed in this paper is a modified digital chaotic sequence generator based on chaotic logistic systems with a coupling structure where one chaotic subsystem generates perturbation signals to disturb the control parameter of the other one. The numerical simulations show that the length of chaotic orbits, the output distribution of chaotic system, and the security of chaotic sequences have been greatly improved. Moreover the chaotic sequence period can be extended at least by one order of magnitude longer than that of the uncoupled logistic system and the difficulty in decrypting increases 2128*2128 times indicating that the dynamical degradation of digital chaos is effectively improved. A field programmable gate array (FPGA) implementation of an algorithm is given and the corresponding experiment shows that the output speed of the generated chaotic sequences can reach 571.4 Mbps indicating that the designed generator can be applied to the real-time video image encryption.

A Scalable De-centralized Multicast Key Management Scheme

Key management is an important part of secure multicast. Among the representative solutions to the multicast key management, the de-centralized scheme inherits the merits of others. In this paper, we present a scalable de-centralized multicast key management scheme, introduce the main idea and analyze its advantages and disadvantages. We construct a core tree in the group member at first, whose nodes sharing a DEK and then constituting one key management level. The core node and other members in the same region form another key management level. When the member in the subgroup changes, only local sub-tree re-key. If the member in the core tree changes, the DEK of the core tree is updated. Thus the overhead of re-key decreases. When data are transmitted between different subgroups, the nodes in the core tree decrypt/encrypt data only once before switch it to local subgroup members, thus the cost of data transmission is decreased. When the size of group becomes large, we use batch re-key scheme to alleviate the cost of re-key further. The scheme has highly robustness, good scalability and lower cost

An Anti-Forensic Algorithm of JPEG Double Compression Based Forgery Detection

Nowadays, a number of forensic algorithms have been developed to detect the manipulations of digital images. However, little consideration has been given to anti-forensic schemes capable of fooling the forensic methods. Aiming at this situation, a novel anti-forensic algorithm is proposed to counter a forensic analysis that can detect double JPEG compression with the same quantization matrix, and the limitation of existing image forensics are illustrated accordingly. The proposed algorithm allows generating tampered images without overall recompression, therefore eliminates the double quantization artifacts which will generally exist in tampered JPEG images. Experiment results show that the tampered images generated by the presented method not only have a good disguise effect, but can also effectively counter the forgery detection method that is based on the detection of double JPEG compression with the same quantization matrix.

A dynamic statistical model for geospatial data access laws based on cloud computing

The strategy of storage and organization can be adjusted utilizing the access and distribution law of the spatial data, which will significantly improve system performance of spatial data services. The access and distribution law of the spatial data based on Hotmap and Zipf-like are statics, and can not reflect its global information real-time. A dynamic statistical method based on collaborative cloud is proposed in this paper to resolve above-mentioned problems. The nodes service capabilities are calculated in our algorithm. The node agents with good service capabilities are chosen preferentially in the group to fuse dynamic statistical information. The experimental results show that the performance of our algorithm can be improved by about 29% compared with the algorithm of random nodes. The algorithm can meet the need of dynamic statistics in large scale cloud mode with high efficiency.

A dynamic method for metadata partitioning based on intensive access of spatial data

In the object-based storage architecture of spatial data, accesses to metadata are 50% to 80% of the total data accesses, so metadata management and partitioning are very important. However, many typical and traditional methods for metadata partitioning, such as directory subtree partitioning, hashing partitioning, etc., should face the issues of hotspot and load balancing. In this paper, we analyzed the accesses to spatial data that follows Zipf-like distribution and has locality of reference, and proposed a dynamic method for metadata partitioning based on intensive access pattern of spatial data. This method considered the temporal locality and spatial locality of accesses to tile, put forward tile access rank algorithm based on the sum of access times per interval time, and got tile access probability by Zipf-likes law for dynamic hashing partitioning of metadata. The experiment results presented the improving of efficiency in tile access rank, and showed that the method for metadata partitioning is an effective solution for hotspot and load balancing issues.

An Active-Passive Security Protection Method for Remote Sensing Image

An active-passive security protection method for remote sensing image is proposed in the paper. High strength content encryption method is used to protect the security of remote sensing image in the process of storage and transmission. The encryption side only need to encrypt the image once, users can get different fingerprinting image by decrypting the image with different keys. If user leaks the decrypted image, they will be identified by embedded fingerprinting information. Considering the remote sensing images special requirements to embed fingerprinting, a way to control the strength of embedded fingerprinting is proposed to reduce the influence to the application of remote sensing image.

A Scalable Conference Key Management Scheme

The most important part of a secure conference is conference key management (CKM). Among its representative schemes, the de-centralized one inherits the merits of others. But current solutions are not very suitable for some real-time multicast applications such as videoconference, etc. In this paper, we present a scalable de-centralized CKM scheme, which called DCKM, the main idea is introduced and its advantages are analyzed. With our scheme, the problem of low efficiency in data transmission caused by multiple encryptions/decryptions in existing de-centralized schemes is solved, the data transmission efficiency is improved a lot, and the data latency is reduced. The forward/backward secrecy of conference is guaranteed, too. The DCKM is a secure, robust, scalable, high data transmission efficiency, cost effective CKM scheme.