Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2022-05-11 Cooperative journals: 《计算机应用研究》
Abstract： Aiming at the problems that the Raft algorithm cannot resist the attacks of Byzantine nodes and the logs are easy to tamper with, this paper proposes an RB-Raft (Resist Byzantine-Raft) algorithm that resists Byzantine nodes. Firstly, this paper uses the method of hash chain to iteratively hash each log. At the same time, verification of the log through the dynamic verification mechanism, so that the malicious behavior of the leader node has a certain fault tolerance rate, which solves the problem of log forgery and verification. Secondly, this paper proposes a "Legacy" mechanism based on threshold encryption, which makes it legal for Candidate nodes to pull votes. This mechanism can prevent Byzantine nodes from randomly the attack of pulling votes to replace leader nodes, and solves the problem that Byzantine nodes affect the system consistency. The experimental results show that the proposed RB-Raft algorithm has the ability to resist Byzantine nodes, and its log recognition rate can reach 100%. At the same time, compared with PBFT, the consensus latency of the algorithm in this paper is reduced by 53.3%, and the throughput is increased by 61.8%. The algorithm proposed in this paper is suitable for consensus in untrusted consortium chains.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2019-04-01 Cooperative journals: 《计算机应用研究》
Abstract： In order to solve the weakness of existing medial image encryption algorithm based on chaotic system in considering the image’s texture feature, this paper proposed a medical image encryption and decryption method based on chaotic mapping and adaptive partitioning. Firstly, it used the 2D Sine Logistic chaotic system to generate two secure sequences with good chaotic characteristics. Then, it divided the original medical image into fixed size image blocks, and calculated their maximum pixel difference and variance. According to the given threshold, it divided these image blocks into texture smooth blocks and texture complex blocks. Finally, it used the first chaotic sequence with ciphertext feedback mechanism to encrypt the smooth blocks, and encrypt the complex blocks by using the second chaotic sequence with plaintext feedback mechanism. Therefore, it obtained the encrypted image. Because the presented algorithm efficiently considers the texture characteristics of image blocks and optimizes the algorithm of chaotic encryption, it improves the encryption and decryption efficiency of medical images. Experimental simulation results show that the presented algorithm has high security and encryption efficiency. Compared with the existent method, it reduces the encryption and decryption time by about 0.5 times. The presented algorithm is suitable for real-time medical images encryption and decryption with big data size.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2019-01-03 Cooperative journals: 《计算机应用研究》
Abstract： There exists several issues in traditional collaborative filtering algorithms: a) It has the sparsity of user rating matrix; b) It ignores the relationship between item attributes. Considering all these problems, this paper proposed a novel collaborative filtering algorithm combining score ratio factor and item attribute. The algorithm used the scoring matrix to obtain the ratio matrix of common and non-common score users between items. Therefore, it increased the influence degree of the users of the item common score, and reduced the error caused by the sparsity of the user-item scoring matrix on the item similarity calculation. quantifying the item attribute could obtain the weight of the item similarity, and it also improved the accuracy of the item similarity calculation. According to the above two points, an algorithm combining scoring scale factor and item attribute weight as item similarity weight is proposed. Experimental results show that, it improved the recall rate and accuracy of the algorithm by 5.1% and 4.7% respectively compared with the existing methods. The algorithm is suitable for personalized recommendation of e-commerce websites.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-12-13 Cooperative journals: 《计算机应用研究》
Abstract： Aiming at the shortage of medical images encryption algorithm in efficiency and security, this paper proposed a novel medical image encryption algorithm in frequent domain based on 2D sine Logistic chaotic mapping. Firstly, the proposed algorithm used the integer wavelet transform of LeGall5/3 to transform medical image from frequent domain to spatial domain. In this way, the high correlation among pixels has disappeared. Then, the proposed algorithm utilized 2D sine logistic chaotic mapping to generate the chaotic sequences. In order to improve the encryption efficiency, this algorithm chose the low frequency coefficients of three-level decomposed to encrypt with chaotic diffusion and scrambling mechanism. In the same time, this algorithm also selected the medium-high frequency coefficients of two-level decomposed to encrypt by chaotic diffusion mechanism for solving the problem of obvious outline in encrypted image. Finally, this algorithm transformed the encrypted wavelet coefficients by the inverse integer wavelet transform and obtained the encrypted image. Experimental simulation results demonstrate that the proposed algorithm is able to protect medical images with low time complexity and a high security level. Compared with the existing spatial method, it reduces the encryption time by about 0.025 times. In addition, the proposed algorithm has better image imperceptibility as well as an excellent encryption efficiency compared to the existing frequent method.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-05-20 Cooperative journals: 《计算机应用研究》
Abstract： For a low capacity of the watermarking algorithm based on the gray scale symbiosis matrix, this paper would introduce the image watermark algorithm which combines texture complexity with DCT-domain JND model. Firstly, it divided the original image into several blocks, and the blocks the texture complexity would be calculated by four texture features of GLCM of each block. The blocks would be sorted based on the texture complexity to locate the blocks of watermark embedding. After that, the prime matrix of original image would be transformed into DCT domain and, combined with new partition way, JND value of each block would be calculated. The mode of watermark embedding would be determined on the basis of JND value and new rules of embedding. The experimental results show that In the same capacity of watermark embedding, the average peak sinal-to-noise ratio(PSNR) of the image in this method is 4.27% higher than existing mathods, when embedding a watermark that is twice the upper limit of the capacity of the original method, the average PSNR of the image is still 53.4498 dB.
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