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    20 April 2022 Volume 49 Issue 2
      
    Information and Communications Engineering
    Low complexity preamble detection algorithm in the low SNR region
    ZHANG Yang,ZHENG Guotian,ZHANG Jian,PANG Lihua,LUAN Yingzi
    Journal of Xidian University. 2022, 49(2):  1-10.  doi:10.19665/j.issn1001-2400.2022.02.001
    Abstract ( 450 )   HTML ( 232 )   PDF (2112KB) ( 345 )   Save
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    Aiming at the contradiction between achievement of an enhanced detection performance by increasing the correlation length of the traditional time-domain direct correlation detection algorithm and its associated hardware implementation feasibility,a joint segment correlation and selective RAKE (JSC-SRAKE) preamble detection algorithm is proposed.Specifically,this algorithm reduces the complexity of hardware implementation by utilizing the concept of segment correlation,and employs RAKE receiving technology to collect the multipath signals to increase the detection signal energy.MATLAB simulation results show that both the probabilities of the missed detection and the false alarm of our proposal are less than 10-4 when the SNR equals -17 dB.At the same time,the proposed algorithm increases the optional range of the optimal decision threshold after introducing the selective rake receiving algorithm,thereby reducing the impact of improper selection of the decision threshold on the detection performance.Compared with direct correlation detection and segment correlation detection,this algorithm has an improved gain in a low SNR region.Moreover,the resources consumed by the proposed algorithm are less than those by the existing algorithms.Although the algorithm increases the complexity,the gain it brings is huge.The algorithm proposed in this paper can achieve the optimal compromise between performance and cost while satisfying the detection performance.Finally,the algorithm is implemented by FPGA in the Single Carrier Interleaved Frequency Division Multiple Access (SC-IFDMA) system,with the results being consistent with those of MATLAB,indicating that the algorithm can be applied to multi-user communication systems with a similar low SNR.

    Adaptive sink-routing decision algorithm for minimum-energy consumption
    SUN Zeyu,LAN Lan,ZENG Cao,LIAO Guisheng
    Journal of Xidian University. 2022, 49(2):  11-20.  doi:10.19665/j.issn1001-2400.2022.02.002
    Abstract ( 230 )   HTML ( 23 )   PDF (1060KB) ( 69 )   Save
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    During the data transmission in wireless sensing networks (WSNs),the data accumulation in the communication link will lead to frequent data collisions,which further consumes the network energy.To address this problem,we propose an adaptive sink-routing decision algorithm for minimum-energy consumption (ASD-MC).First,when the data fusion degree is between the maximum and minimum value,the aggregation gain is exploited to calculate the proportional relationship between the data fusion degree and node distance-related parameters.Then,we discuss the correlation among different nodes with three distance correlation coefficients.When multiple nodes do not conduct data fusion,the condition for the existence of data fusion degree is proved for the next-hop node.In addition,according to the functional relationship of data compression energy ratio,we consider the data compression and decompression process on the link both at the source node and at the sink node.Then the procedure for the calculation of the network energy consumption is provided.Based on the above analysis,we employ the energy conversion model to derive the necessary condition for the Euclidean distance between any two nodes.Furthermore,the procedure for the implementation of our proposed algorithm is also presented.Finally,simulation results show that,compared with existing algorithms,our proposed algorithm could reduce the network energy consumption and the average network delay by 10.29% and 12.57%,respectively,which verifies the effectiveness and validity of the ASD-MC algorithm.

    Joint pilot and Viterbi decoding synchronization technology in high-dynamic environments
    GUAN Lei,SI Jiangbo,LI Zan,LIU Xiaoxu,DONG Chao
    Journal of Xidian University. 2022, 49(2):  21-28.  doi:10.19665/j.issn1001-2400.2022.02.003
    Abstract ( 282 )   HTML ( 19 )   PDF (959KB) ( 74 )   Save
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    Since the Doppler frequency offset and Doppler rate-of-change caused by the accelerated motion of the moving targets are hard to tract and eliminate in high-dynamic environment,which seriously affects the performance of the receiver,we propose a carrier synchronization method for joint pilot and Viterbi decoding per-survivor-processing (PSP).First,an open-loop acquisition is performed based on the minimum mean square error (MMSE) principle,and the frequency offset is modeled in the form of the Taylor series expansion.Then,a known sequence is used to estimate the Doppler frequency offset and Doppler rate-of-change,thereby limiting the frequency offset and rate-of-change to a small range.Meanwhile,to overcome the performance degradation caused by the accumulation of long-term phase errors,the closed-loop tracking is implemented by the PSP technology,and the soft information determined by Viterbi symbol-by-symbol is input to the third-order phase-locked loop (PLL).Moreover,the frequency synthesizer is adjusted according to the error of the phase detector.Then this action is iteratively performed to minimize the error of the phase detector and realize the carrier synchronization.Finally,coherent demodulation reception is achieved.Simulation results show that when the normalized frequency offset is less than 0.1 and the normalized rate-of-change is less than 10-3,the proposed method can track the carrier accurately.Furthermore,under the bit-to-error (BER) constraint of 10-5,there is only 0.8dB difference in S/N ratio between the proposed decoding synchronization cascade tracking algorithm and the ideal carrier synchronization without the Doppler frequency offset and rate-of-change.In addition,the propose algorithm is significantly superior to the traditional phase-locked loop and MMSE algorithm.

    Novel dual-band multi-polarized shared-aperture waveguide antenna array
    LU Jiaguo,ZHANG Hongtao,WANG Wei,ZHANG Bing,YIN Yingzeng
    Journal of Xidian University. 2022, 49(2):  29-35.  doi:10.19665/j.issn1001-2400.2022.02.004
    Abstract ( 408 )   HTML ( 91 )   PDF (2756KB) ( 108 )   Save
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    An efficient technique for realizing dual-band multi-polarized waveguide antenna array featuring in shared-aperture,low-profile,light-weight and high radiation efficiency is proposed.A rectangular cavity-backed slotted antenna is adopted to realize L-band vertical polarization,while the C-band horizontal and vertical polarization are realized by utilizing the ridged waveguide slotted antenna.The L-band antenna is located between two C-band vertical-polarized slotted waveguides and below a C-band horizontal-polarized waveguide.To achieve a more miniaturized volume of the shared-aperture antenna array,an efficient feeding design of a metal bridge is introduced into the L-band rectangular waveguide.In order to confirm the feasibility of the proposed design,an array prototype with 8×16 elements operating in the C-band and 2×2 elements operating in the L-band is fabricated and measured.Experimental results demonstrate that the proposed antenna array has a satisfactory impedance bandwidth of 12% in the L-band and that of 5.5% in the C-band with VSWR<2,and the antenna radiation efficiency of above 85% for both frequency bands.

    Design of an online caching scheme in fog networks
    SUN Rong,ZHENG Huihui,LIU Jingwei
    Journal of Xidian University. 2022, 49(2):  36-41.  doi:10.19665/j.issn1001-2400.2022.02.005
    Abstract ( 218 )   HTML ( 14 )   PDF (648KB) ( 38 )   Save
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    Driven by the vision of 5G communications,an efficient solution which applies the coded caching technology to obtain data quickly in fog networks is proposed.First,this paper models the cache architecture based on the fog computing networks as the two-hop network,and proposes a decentralized online coded caching scheme based on file splitting and MDS encoding for the two-hop network.This scheme ensures that the cache content of relays and users is consistent with the files in the server by updating the server files and updating the cache content of relays and users,so as to maintain the validity of the cache content.We then analyze the tradeoff between the cache memory and the traffic load for two-hop networks where each relay and user has limited cache memories.Simulation results show that the proposed schemes have a low transmission load and can relieve network congestion effectively.

    MIMO wireless covert channel based on precoding
    CAO Pengcheng,LIU Weiwei,LIU Guangjie,MAO Weiwei,DAI Yuewei
    Journal of Xidian University. 2022, 49(2):  42-49.  doi:10.19665/j.issn1001-2400.2022.02.006
    Abstract ( 200 )   HTML ( 90 )   PDF (2335KB) ( 49 )   Save
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    To conceal the existence of secret information,the wireless covert channel established in modulation of the physical layer converts secret information into artificial noise for transmission.In multiple-input multiple-output (MIMO) communication scenarios,due to the openness of the transmission medium,the detector can use the correlation of each antenna signal to discover the covert channel.To solve this problem,this paper proposes a MIMO wireless covert channel based on precoding.Assuming that both the sender and detector can obtain the MIMO channel state information (CSI),the sender can use this CSI to pre-encode the generated artificial noise to remove correlation of the multiple signals received by the detector.The receiver can generate the precoding matrix through the CSI transmitted through the public channel,and then extract secret information.Simulation results show that compared with the existing method,the proposed MIMO wireless covert channel removes the correlation of the multiple signals received by the detector,and effectively improves the undetectability,and that the reliability has been improved to a certain extent.

    All-optical photonic microwave measurement approach based on the Sagnac loop and I/Q detection
    KANG Bochao,FAN Yangyu,TAN Qinggui,GAO Yongsheng
    Journal of Xidian University. 2022, 49(2):  50-57.  doi:10.19665/j.issn1001-2400.2022.02.007
    Abstract ( 226 )   HTML ( 18 )   PDF (1660KB) ( 36 )   Save
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    For high-speed wireless communication,the Internet,new-generation radar system and real-time signal processing system,microwave measurement systems with a large instantaneous bandwidth (greater than 10GHz) and wide working frequency range (several MHz to several hundred GHz) are required.To meet these demands,a simple and novel optical approach to implementing the broadband measurement approach is proposed.In the experiment,the Doppler frequency shifts are estimated with clear direction discrimination and high resolution with the max error of 8 Hz.Then,the approach is applied for phase detection,and the phase shifts are successfully measured and estimated for microwave signals with the operating frequency ranging from 10 to 40 GHz.The max error of phase measurement is calculated to be less than 7 degrees.The approach is simple,easy to implement,multifunctional and tunable,so that it can provide a more competitive approach to realizing the measurement of the microwave signals for future wideband electronics applications than electronic solutions.

    Novel unambiguous tracking algorithm for BOC and its derivative signals
    SUN Xiyan,SONG Shaojie,JI Yuanfa,LIANG Weibin,LI Youming
    Journal of Xidian University. 2022, 49(2):  58-66.  doi:10.19665/j.issn1001-2400.2022.02.008
    Abstract ( 199 )   HTML ( 14 )   PDF (1987KB) ( 44 )   Save
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    Aiming at the tracking ambiguity problem caused by the multi-peak characteristic of the Binary Offset Carrier and its derivative signals autocorrelation function,this paper proposes an unambiguous tracking algorithm based on the characteristics of the signal correlation function.First,the general expression for the cross-correlation function for the BOC reference and derivative modulation signal is obtained by the shape code vector constructed in this paper.The pseudo code of the received signal is used as a local reference signal,and a special local code waveform is designed to perform correlation operations with the corresponding received signal to obtain a signal correlation sub-function.Then,the sub-functions are recombined using the reconstruction rules proposed in this paper,and the edge peaks are completely eliminated and a new correlation function with a single peak is retained.The code tracking loop structure of the improved tracking algorithm,compared with the traditional code tracking loop structure,reduces the filter circuit,the structure is simplified,and the hardware implementation complexity is also reduced.Simulation results show that the secondary peak of the correlation function is eliminated while retaining the sharpness of the main peak.By comparing with the traditional tracking algorithm,it can be seen that the code tracking accuracy of this algorithm is higher under the premise of the same carrier-to-noise ratio.The phase discrimination function does not have any false lock points except the zero crossing point,and will not cause a false lock problem.Compared with the traditional tracking ambiguity elimination algorithm,this method can effectively apply BOCs(m,n) and CBOC(6,1,1/11) signals without ambiguity tracking.

    Resource allocation mechanism with energy consumption awareness in the edge enhanced H-CRAN
    LV Yi,WANG Yanbin,ZHANG Hong,WANG Ruyan,ZHANG Puning
    Journal of Xidian University. 2022, 49(2):  67-78.  doi:10.19665/j.issn1001-2400.2022.02.009
    Abstract ( 193 )   HTML ( 11 )   PDF (1801KB) ( 53 )   Save
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    Focusing on the shortcomings of low resource utilization rate,high equipment energy consumption and deterioration of user service quality in the mobile edge computing enhanced heterogeneous cloud radio access network at present,an energy consumption aware communication and computing resource allocation mechanism is proposed from the perspective of spectrum resources and computing resources.First,taking the network throughput as the revenue and energy consumption as the cost expenditure,a profit model framework from the perspective of service providers is established.In order to avoid the waste or overload of edge server resources caused by uneven resource allocation,the network throughput is first improved by analyzing various service requests coming from users and reasonably allocating spectrum resources by using the sparse matrix algorithm.For computing resources,a heuristic algorithm is designed to determine user association and user computing resource demand,so that each edge server can be fully utilized.Based on the results of resource utilization and considering the capacity constraints of the optical fiber forward link,the mobile edge computing server can be dynamically deployed at the macro base station or remote radio heads to reduce the equipment overhead.Simulation results for different parameter indexes and service requests at different times of a day show that the proposed mechanism can effectively increase network throughput,reduce network energy consumption and decrease the blocking probability of the optical fiber forward link,so that this mechanism is apparently superior to other algorithms.

    Dynamic scheduling method for service function chains in space air terrestrial aided edge cloud networks
    QIAO Wenxin,LU Yu,LIU Yicen,LI Zhiwei,LI Xi
    Journal of Xidian University. 2022, 49(2):  79-88.  doi:10.19665/j.issn1001-2400.2022.02.010
    Abstract ( 315 )   HTML ( 19 )   PDF (2274KB) ( 67 )   Save
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    As a new network architecture,the space air terrestrial integrated network has the advantages of wide network coverage and ubiquitous seamless access ability,but it also faces the contradiction between increasing users’ demands and limited network service resources.Introducing edge computing into space air terrestrial integrated networks can greatly improve the system’s business processing capability.Meanwhile,first,in order to improve the resources utilization of Space Air Terrestrial aided Mobile-access Edge Cloud (SAT-MEC) networks,and provide users with diversified and high-quality network services,we connect a group of virtual network functions according to a certain business logic,which forms a dynamic and reconfigurable service function chain.Considering the high dynamic and heterogeneous characteristics of the SAT-MEC network,the efficient scheduling method for its dynamic service function chain is studied,and the system model of the SAT-MEC network is designed.On this basis,the objective function of end-to-end delay optimization constrained by network resources and service requests is constructed.Second,combining the advantages of efficient parallel computing of Quantum Machine Learning,the path selection problem of the service function chain is modeled as a Hidden Markov Model based on Open Quantum Random Walk,with the model solved by the Quantum Backtrack Decoding method.Compared with the traditional precise solution and heuristic methods,simulation results show that the proposed method can improve the success rate of service request and reduce the end-to-end average delay under the condition of a high network traffic load.

    New distributed positioning algorithm for sensor nodes
    XU Shasha,ZHOU Fang,LI Yangjian,JIANG Junzheng
    Journal of Xidian University. 2022, 49(2):  89-96.  doi:10.19665/j.issn1001-2400.2022.02.011
    Abstract ( 306 )   HTML ( 20 )   PDF (1088KB) ( 76 )   Save
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    The node localization problem in large scale wireless sensor networks can be formulated into a highly nonlinear nonconvex optimization problem which is hard to solve directly in large scale sensor networks.This paper proposes a new distributed localization algorithm to solve this problem.First,the global undirected graph composed of the large scale wireless sensor network is decomposed into a series of partially overlapping subgraphs,and then the global optimization problem is decomposed into a series of small scale subproblems for iterative solutions.The optimization problem in each subgraph can be solved iteratively independently.The new distributed localization algorithm for sensor nodes consists of two steps in each iteration,First,the Barzilai-Borwein gradient method is used to estimate the location of the node in the divided partially overlapping subgraph.The gradient method has a low computational cost and greatly speeds up the convergence.Second,the same sensor nodes in different partially overlapping subgraphs are fused and averaged.Theoretical analysis and simulation results show that compared with the existing methods,the proposed new distributed localization algorithm has a higher scalability and localization accuracy in large scale wireless sensor networks,and can be used for localization in large scale sensor networks.

    Analysis of the outage performance of the cooperative V2X with the power-constrained CR-NOMA
    QIAO Yuhang,ZHANG Liangmei,HE Yucheng,ZHOU Lin
    Journal of Xidian University. 2022, 49(2):  97-107.  doi:10.19665/j.issn1001-2400.2022.02.012
    Abstract ( 218 )   HTML ( 13 )   PDF (3913KB) ( 43 )   Save
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    Considering the application of wireless information and energy transmission in the underlying cognitive non-orthogonal multiple access network of vehicles,a two-stage relay selection scheme for NOMA networks is proposed according to the statistical characteristics of NOMA networks when the secondary network is interfered by the primary network.In the first slot,the secondary network source node broadcasts superimposed signals to all relays using a fixed power allocation scheme,which is determined by the statistical characteristics of the channel quality of the second hop link.In the second slot,by selecting the optimal relay in two steps based on the signal received at the relay,the selected relay uses the power splitting scheme to perform the SWIPT,and the power collected is used only to forward the decoded signal with the energy consumption of coding and decoding not considered.Two secondary users use successive interference cancellation technology to decode the received superposed signals.At the same time the secondary users are interfered by the primary network signal.Under the limit of the interference temperature constraint,the approximate expression for the interruption probability of each secondary user is derived,and the correctness of the numerical analysis is verified.By analyzing the influence of system parameters on the interrupt probability of secondary users,it is proved that the TSRS scheme is superior to the existing system in improving the interrupt performance.

    Speech enhancement combining the self-adaptive soft mask and mixed features
    ZHANG Min,JIA Hairong,ZHANG Gangmin,WANG Suying
    Journal of Xidian University. 2022, 49(2):  108-115.  doi:10.19665/j.issn1001-2400.2022.02.013
    Abstract ( 211 )   HTML ( 14 )   PDF (1398KB) ( 38 )   Save
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    Aiming at the problem of the loss of effective features when using Mel domain features for speech enhancement,this paper proposes a method to extract the Gammatone domain features of noisy speech using a power function that is more in line with human ear compressive perception,and deep-mix it with Mel domain features for speech enhancement.In order to improve the limitation of the Mel domain filter losing effective features at high frequencies.At the same time,in order to capture the connection between the transient information on the speech and the speech information on the adjacent frames,the differential derivative of the mixed feature is obtained,and the mixed feature is obtained by fusing it with the initial feature.Second,since traditional time-frequency masking cannot be automatically adjusted according to the difference in the signal-to-noise ratio,the intelligibility of an enhanced speech is affected.In order to improve the speech quality while improving the speech intelligibility,a soft mask that can be adjusted adaptively according to the signal-to-noise ratio information is proposed,and the phase difference information of the voice is incorporated.Finally,experiments are conducted on multiple speeches under different noise backgrounds.Experimental results show that when using mixed features and self-adaptive soft masks for speech enhancement,the subjective speech quality and short-term objective intelligibility of the enhanced speech can be improved,which verifies the effectiveness of the proposed algorithm in this paper.

    Invulnerability measurement for the C4ISR network based on information flow betweenness centrality distribution entropy
    YU Changren,JIA Lianxing,ZHANG Bin
    Journal of Xidian University. 2022, 49(2):  116-124.  doi:10.19665/j.issn1001-2400.2022.02.014
    Abstract ( 217 )   HTML ( 10 )   PDF (1352KB) ( 26 )   Save
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    Currently,many researches on invulnerability focus on statistical analysis of the network structure which is not suitable for the C4ISR network with specific functions.In view of this problem,this paper proposes “information flow intermediate number centrality distribution entropy” to measure the invulnerability of the C4ISR network.It goes from the perspective of the function of information flow and uses the theory of “intermediate number centrality of complex networks” and “information entropy”.The shortest information path from reconnaissance node to attack node is regarded as an operational information chain,and the “information flow intermediate number centrality ” is proposed to measure the number of operational information chains passing through a node in the C4ISR network.The uniformity of information flow intermediate number centrality is measured by “information flow intermediate number centrality distribution entropy”,and the effectiveness of this index is analyzed which can reflect the invulnerability of the C4ISR network function.Based on a representative C4ISR network structure,the invulnerability of the network after random attack,degree attack,intermediate number centrality attack and information flow attack is simulated,with the application of information flow intermediate number centrality distribution entropy in improving the invulnerability of C4ISR network functions also analyzed.Simulation results show that this indicator is more sensitive and accurate than structural invulnerability indicators such as average network efficiency of complex networks,natural connectivity,degree distribution entropy,intermediate number centrality distribution entropy,and so on and that it can find the critical point of C4ISR network function failure,and can provide guidance for improving the functional invulnerability of the C4ISR network.

    Timing and area optimized re-configurable network-on-chip router
    HU Dongwei,SHANG Delong,ZHANG Yong,WANG Linan
    Journal of Xidian University. 2022, 49(2):  125-134.  doi:10.19665/j.issn1001-2400.2022.02.015
    Abstract ( 193 )   HTML ( 11 )   PDF (2090KB) ( 20 )   Save
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    The Network-on-Chip Router is the key component of multi/many-core processors.In this paper,firstly the schematic architectures of the synchronous First-Input-First-Output (FIFO) buffer and asynchronous FIFO buffer are reviewed with their latencies addressed.Then the architectures of the Network-on-Chip (NoC) and its router are introduced.With the previous foundations,an optimized clock tree distribution scheme,as well as the NoC router implementation under this clock tree distribution scheme,are proposed.With this novel clock tree optimization,the latency of the NoC is greatly reduced.In addition,in order to decrease the area of the register based FIFO,the latch based FIFO is proposed.Single tick latch writing is ensured.And sharing multiple FIFOs is proposed.The proposed techniques are especially useful for embedded low-power many-core processors.

    Computer Science and Technology & Cyberspace Security
    Decentralized ciphertext sharing based on blockchain
    ZENG Huixiang,XI Ning,XIE Qingqing,LV Jing,CUI Zhihao,MA Jianfeng
    Journal of Xidian University. 2022, 49(2):  135-145.  doi:10.19665/j.issn1001-2400.2022.02.016
    Abstract ( 255 )   HTML ( 22 )   PDF (1734KB) ( 93 )   Save
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    The cooperation between smart devices has greatly enriched various applications of smart homes.Due to the frequent information sharing between devices,users' data suffer from security threats such as data theft and tampering.The ciphertext-policy attribute-based encryption (CP-ABE) scheme realizes the secure sharing of cloud data across users and devices while keeping confidential to the cloud service provider.However,the limited resources of smart devices and the risk of a single point of failure in the attribute management server have brought serious challenges to the traditional secure sharing of ciphertext data.Therefore,we propose a decentralized ciphertext data security sharing scheme based on the block chain and outsourcing decryption CP-ABE.We construct a consortium blockchain network with attribute centers as nodes and record attribute and ciphertext information through the blockchain.The blockchain realizes the decentralized management on user’s attributes,on the basis of which,combined with the outsourcing decryption CP-ABE technology,the computation of smart devices is reduced and the efficiency of sharing is improved.Experimental and analytical results show that the scheme can reduce the computing burden of smart devices and ensure the security of data sharing.

    Self-equivalence encodings and improvements of white-box implementations
    LUO Yinuo,TONG Peng,CHEN Jie,DONG Xiaoli
    Journal of Xidian University. 2022, 49(2):  146-154.  doi:10.19665/j.issn1001-2400.2022.02.017
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    In the white box attack environment,the attacker can not only access the input and output of the cryptographic algorithms,but also obtain the internal details of the algorithms and control the terminal.In this environment,CHOW et al.constructed the look-up tables by using network encodings,embedded the key in the look-up tables,and designed the white-box implementation scheme for the AES algorithm and DES algorithm.The white-box implementation of the cryptographic algorithm based on self-equivalent encodings design is a new implementation method.RANEA et al.designed a white-box implementation scheme for substitution replacement cipher by using the self-equivalent encodings of the S-box.The size of encoding space completely depends on the S-box self-equivalence of the cipher,and the security analysis also shows that the application scope of this scheme is limited.In view of this situation,this paper considers the impact of self-equivalence of the S-box on the security of white-box implementation,and proposes two improved schemes for expanding the encoding space of the white-box implementation scheme by adding self-equivalence encodings to the linear layer or linear encodings to the affine layer.Security analysis shows that the two improved schemes can effectively resist the attacks from RANEAet al,and expand the application scope of the scheme.Finally,based on the above two design schemes,this paper constructs two white-box implementations of the AES algorithm,and compares the security with the white-box AES scheme of RANEA et al.The comparison results show that the two improved schemes can resist protocol attacks based on the centralization problem and asymmetric problem.

    Improved violent behavior detection method for the R(2+1)D network
    WANG Yong,JIN Weizhao,FENG Wei,QUAN Yinghui
    Journal of Xidian University. 2022, 49(2):  155-163.  doi:10.19665/j.issn1001-2400.2022.02.018
    Abstract ( 202 )   HTML ( 11 )   PDF (3125KB) ( 34 )   Save
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    In public security,the complex violence behavior detection is of important research value.Traditional methods are mainly based on hand-crafted features,but they have a limited generalization ability.The existing deep learning network models have a better tolerance,but those kinds of methods face the challenge of obtaining a high accuracy.To solve the above problems,a novel violent behavior detection method is proposed in this paper by combining an improved R (2+1) D network and the dense connection idea.In the branch of the traditional R (2+1) D residual module,the three-quarters of the feature map is ignored due to the convolution operation with strides of 2.In this paper,the convolution operation is optimized for a pooling operation and a convolution operation with strides of 1,and the detection accuracy is increased by 2.3%.Besides,the dense connection idea is adopted into the residual module to establish the connection between different convolutional layers.The improvement could alleviate the problem of gradient dissipation during the training process,and the detection accuracy is further improved by 1.46%.Experimental results on one public dataset and one self-built dataset demonstrate the effectiveness of the proposed method for the complex violence behavior detection.

    Video steganography based on macroblock complexity
    YANG Xiaoyuan,TANG Hongqiong,NIU Ke,ZHANG Yingnan
    Journal of Xidian University. 2022, 49(2):  164-172.  doi:10.19665/j.issn1001-2400.2022.02.019
    Abstract ( 166 )   HTML ( 16 )   PDF (1617KB) ( 31 )   Save
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    The video steganography based on the motion vector (MV) usually destroys the local optimality MV,and the destruction of such statistical properties is easily detected by the corresponding steganography analytical algorithms,resulting in a reduced performance of anti-stegoanalysis and steganography security.In order to reduce the damage to the local optimality of MVs,a video steganography algorithm based on macroblock complexity is proposed through the analysis of the influence of MV modification on the video quality and the local optimality of MV,and the low-complexity macroblock motion vectors are selected as carriers to effectively maintain the local optimality after embedding information.The proposed algorithm first introduces the Hilbert filling curve to scan macroblock pixels and defines macroblock complexity,then the macroblock complexity distribution is counted and the embedding threshold is dynamically determined according to the length of to-be-embedded data,and finally selects the MV of macroblock whose complexity is lower than the embedding threshold for random matching modification to embed secret information.Experimental results show that the stego video PSNR and SSIM degradation of the proposed algorithmare no more than 0.30 dB and 0.04,respectively,and the bit rate increase does not exceed 0.97 % when the video is compressed and embedded with a compression rate of 1000 Kb/s.Its comparison with related algorithms show that the stego video of the proposed algorithm has a high-level visual quality and a low-level bit rate growth,and that the proposed algorithm has good anti-steganalysis detection capability and security.

    Latent feature reconstruction generative GAN model for ICS anomaly detection
    GU Zhaojun,LIU Tingting,SUI He
    Journal of Xidian University. 2022, 49(2):  173-181.  doi:10.19665/j.issn1001-2400.2022.02.020
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    The anomaly detection of most of the industrial control systems (ICS) is faced with the problem of class-imbalance,which leads to a decrease in accuracy and the deterioration of generalization.According to the generative adversarial network (GAN),this paper proposes an anomaly detection model using only normal samples for training——the latent feature reconstruction generative GAN model (LFR-GAN).In the training stage,the model learns to generate the mapping of data to the latent space by a new encoder for realizing latent space feature reconstruction.In addition,an SE Block module is embedded to enhance the effective feature weight and to improve the ability of latent space feature reconstruction.For the discriminator,it identifies three data pairs produced by two encoders and one generator simultaneously,improving the model accuracy and generalization ability.In the detection stage,considering the reconstruction and identification of losses comprehensively,anomaly scoring formula optimization based on the L2 norm is adopted to overcome mode collapse.The validation experiment results on SWaT and WADI datasets show that the LFR-GAN model has obvious advantages over other GAN models in terms of learning ability,stability and detection results.

    DorChain:Utilization of dormant coins to improve the transaction verification efficiency
    PAN Senshan,XU Lamei
    Journal of Xidian University. 2022, 49(2):  182-189.  doi:10.19665/j.issn1001-2400.2022.02.021
    Abstract ( 167 )   HTML ( 10 )   PDF (1692KB) ( 52 )   Save
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    In response to the problem of the increased verification overhead caused by the increasing growth of the UTXO (Unspent Transaction Output),a new method of using dormant coins to improve transaction verification efficiency is proposed.The UTXO is divided into two states,active and dormant.The active UTXO is stored in the active set ATXO (Active Transaction Output),and the dormant UTXO is stored in the dormant set DTXO (Dormant Transaction Output).Two technologies-the RSA accumulator and MMR (Merkle Mountain Range) are used to instantiate the dormant and active UTXO respectively,forming DTXO_C (Dormant Transaction Output_Commitment ) and AMR (Active Merkle Root) storage in the block header.In addition,18 months is an epoch and the last block is a checkpoint.Only the DTXO_C is stored in the checkpoint and updated,with the AMR stored in both the normal block and the checkpoint to ensure the latest state of the block.At the same time,the authenticity of the transaction is ensured by constructing the dormancy proof,and it is proved that it is not forged.The evaluation of the program shows that in providing the minimum proof size (320 bytes) and the minimum block header to introduce data (32 B),it only takes about 100 milliseconds to verify 1 000 transactions.This verification method can greatly improve the efficiency of transaction verification.

    Key business node identification model for the business process
    XIE Lixia,NI Huiyu
    Journal of Xidian University. 2022, 49(2):  190-197.  doi:10.19665/j.issn1001-2400.2022.02.022
    Abstract ( 256 )   HTML ( 9 )   PDF (1220KB) ( 29 )   Save
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    Aiming at the problem of business continuity security management,a key business node identification model for the business process is proposed.First,the node set to be evaluated is obtained according to the business process,the node importance evaluation attributes are quantified according to the importance of the business nodes,and the business node importance decision matrix is constructed by combining with the business node set to be evaluated and the value of the business node evaluation attributes.Second,the evaluation attribute weight of business nodes is improved from the subjective and objective dimensions,the importance combination weight decision matrix of business nodes is constructed,the AE-VIKOR (Analytic hierarchy process and Entropy weighting VIKOR,AE-VIKOR) method is used to calculate the importance coefficient of business nodes,and the key node is identified.Finally,when a security event occurs in a system,the effectiveness and accuracy of the model are proved by comparing and analyzing the impact of the implementation of key businesses and the other businesses on business continuity.Experimental results show that the node importance coefficient is calculated by the AE-VIKOR method in the model,and that the key business node is identified according to the node importance coefficient.The experiment further compares and analyzes the impact of key business nodes and other business nodes on business continuity,and compares the identification results of the AE-VIKOR method and other methods and different decision coefficients,with the results showing that the model identification is efficient and accurate.

    Attention driven nuclei segmentation method for cell clusters
    MA Sike,ZHAO Meng,SHI Fan,SUN Xuguo,CHEN Shengyong
    Journal of Xidian University. 2022, 49(2):  198-206.  doi:10.19665/j.issn1001-2400.2022.02.023
    Abstract ( 225 )   HTML ( 15 )   PDF (2207KB) ( 43 )   Save
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    Nuclei morphology of pleural effusion cell clusters provides an essential way for the diagnosis,metastasis,and treatment evaluation of the lung cancer.Accurate segmentation of the nuclei is the basis of pathological diagnosis of the lung cancer.Because of the complex background of tumor cell clusters in pleural effusion,the inhomogeneity of nuclei features (scattered feature information),and nuclei overlapping within clusters (whose characteristics are not prominent),the segmentation of tumor cell clusters is still a challenging problem.In this paper,an improved U-Net model,named CRUNet,based on the attention mechanism is proposed.With the attention module,the CRUNet can enhance the learning of non-salient features of the nucleus from spatial attention and channel attention,and improve the jumping connection of the U-Net to integrate the deep and shallow features of the U-Net to solve the problem of the semantic gap.Experimental results show that compared with other state-of-the-art methods,the CRUNet can achieve a better segmentation performance on our self-established pleural effusion cell cluster dataset.To further illustrate the effectiveness of the proposed network,the CRUNet is also compared with other networks on a public cell dataset-BBBC020.

    Index edge geometric convolution neural network for point cloud classification
    ZHOU Peng,YANG Jun
    Journal of Xidian University. 2022, 49(2):  207-217.  doi:10.19665/j.issn1001-2400.2022.02.024
    Abstract ( 180 )   HTML ( 9 )   PDF (2186KB) ( 42 )   Save
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    Point cloud learning has attracted more and more attention due to its wide application in many scientific fields,such as computer vision,automatic driving,and robot technology.The sparseness,disorder and finiteness of point cloud data present great difficulties to the point cloud classification task based on deep convolutional neural networks.The convolutional neural network often uses operations like voxelization and multi-view.However,the conversion process causes problems of local feature information loss and low computational efficiency.At present,the existing deep learning method oriented point cloud classification which consumes the raw point cloud has the problem of many traning parameters and complex model structures,thus making it difficult to process the real-time task.In order to lightweight the network to realize real-time point cloud classification tasks,on the basis of intensive studies of these problems,an index edge geometric convolution neural network model is proposed in this paper.First,in order to achieve lightweight,the network structure and hyperparameters are trimmed and compressed,respectively.Second,to enhance the accuracy and efficiency of algorithms,a new local region is determined on each convolution layer by using the KNN(K-Nearest Neighbor) algorithm,with the vector direction between adjacent points added,and the output features of each layer are inherited by an index hop link,which further reduces the loss of local feature information.Experiments show that the proposed network can achieve a classification accuracy of 92.78% during 42 min on the ModelNet40.Compared with the DGCNN(Dynamic Graph Convolutional Neural Network),the classification accuracy is improved by 0.58%.With the advantages of high classification accuracy and lightweight,this network model can be deployed in small embedded devices.

    PSO-DE algorithm based on the optimal selection strategy
    ZHANG Dehua,HAO Xinyuan,ZHANG Nina,WEI Qian,LIU Ying
    Journal of Xidian University. 2022, 49(2):  218-227.  doi:10.19665/j.issn1001-2400.2022.02.025
    Abstract ( 168 )   HTML ( 13 )   PDF (3173KB) ( 48 )   Save
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    Aiming at the problems of the population diversity reduction in the late evolution of particle swarm optimization (PSO),and the information exchange error of PSO-DE,this paper presents a PSO-DE algorithm based on the optimal selection strategy.First,a weighted network (WN) is constructed to calculate the systematic biases.Then the optimal selection strategy mechanism is introduced,and the fitness function is constructed as an evaluation criterion.Finally,the systematic deviation estimate is used to register the target sensor measurement.In the test of population diversity and fitness,the algorithm proposed in the paper has a richer population diversity,and the optimal fitness value of the individual is 2.0194×10-5.In the experiments on non-maneuvering and maneuvering targets,the deviation value rapidly converges to the true deviation value after about 2s,with the shortest convergence time being 201.8s,and the RMS error value is reduced by more than 10 times.Simulation results show that the algorithm not only increases the population diversity,but also improves the convergence speed and the accuracy.

    Multi-scale generation antagonistic network for the low-dose CT images super-resolution reconstruction algorithm
    XU Ying,LIU Shuai,SHAO Meng,YUE Guodong,AN Dong
    Journal of Xidian University. 2022, 49(2):  228-236.  doi:10.19665/j.issn1001-2400.2022.02.026
    Abstract ( 330 )   HTML ( 22 )   PDF (2086KB) ( 69 )   Save
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    Low-dose CT can reduce X-ray radiation and damage to human body,but the imaging quality can also be significantly reduced.In order to obtain high quality images with fine structural details,a low dose CT image super-resolution reconstruction algorithm based on the multi-scale residual generation network (MSRGAN) is proposed to recover high resolution (HR) images from low resolution (LR) images with pathology unchanged.First,a residual network is introduced to prevent overfitting while realizing feature reuse.Second,the multi-scale network can make full use of image features of different sizes,enrich image details and improve the utilization rate of features in the reconstruction process.Finally,by combining the adversarial loss and content loss,the reconstructed image with a better perceived quality can be obtained when the generated feature is constrained.Experimental results show that compared with other algorithms,this method improves in SSIM,FSIM and PSNR indexes,that its GAN's IS,FID and SWD performance is better than that of the other two Gan-based algorithms,and that it has a better performance in edge contour detail,which fully proves the effectiveness of this algorithm.