To solve the problem that blockchain technology is difficult to be used in large-scale business scenarios due to storage constraints, a blockchain shard storage model based on threshold secret sharing was proposed. Firstly, the transaction data to be placed in blockchain was processed into shards by consensus nodes using improved Shamir's threshold secret sharing. Secondly, consensus nodes constructed different blocks based on data shards and distributed them to other nodes existing in the blockchain network for storage. Finally, when a node wanted to read transaction data, the node would request data from k of the n nodes with transaction data shards, and use Lagrange interpolation algorithm to recover the original transaction data. The experimental results show that the model not only guarantees the security, reliability and privacy of data to be placed in blockchain, but also effectively reduces the amount of data stored by each node to 1/(k-1), which is conducive to blockchain technology using in large-scale business scenarios.
Aiming at the low efficiency of test case automatic generation technology, an IMproved Bacterial Foraging Optimization Algorithm (IM-BFOA) was proposed with introduction of Knet map. Firstly, Kent map was used to increase the diversity of the initial population and global search of bacteria. Secondly, the step size of chemotaxis stage in the algorithm was adaptively designed to make it more rational in the process of bacterial chemotaxis. Finally, a fitness function was constructed according to the program under test to accelerate the optimization of test data. The experimental results show that compared with Genetic Algorithm (GA), Particle Swarm Optimization (PSO) algorithm and standard Bacterial Foraging Optimization Algorithm (BFOA), the proposed algorithm is the best in terms of iterations number and running time with the guarantee of coverage and has high efficiency of test case generation.
Aiming at the throughput of high-speed railway Multiple Input Multiple Output (MIMO) system has not been fully improved, an adaptive beam transmission scheme based on antenna grouping was proposed. Firstly, the train position information was predicted by the Base Station (BS), and the beamforming technology was introduced into high-speed railway environment to establish a high-speed Massive MIMO three-dimensional model. Secondly, it was verified that in BS antenna grouping situation, the throughput of a sub-beam and its corresponding number of transmit antennas satisfied nonlinear relationship and the number change of sub-beam antennas did not affect the throughput of other beams. Finally, based on the above, an adaptive beamforming scheme based on antenna grouping was used to adjust the number of beams required and the number of transmit antennas required by the sub-beams when the train runed at different locations to ensure optimal system throughput at all the locations. The computer simulation results show that compared with the traditional single-beam, dual-beam and eight-beam schemes, the proposed scheme achieves 87.9%, 62.3%, and 50.6% improvement respectively in system throughput when the distance between the train and the BS is less than 125 m, achieves a similar system throughput of single beamforming when the distance is more than 125 m. The experimental results show that the proposed scheme has best system throughput whether the train is far away from or close to the BS, and is better adapted to high-speed railway environment.
In the cluster-based routing algorithm of Wireless Sensor Network (WSN), "energy hole" phenomenon was resulted from energy consumption imbalance between sensors. For this problem, a hybrid multi-hop routing algorithm of effective energy-hole avoidance was put forward on the basis of the research of the flat and hierarchical routing protocols. Firstly, the concept of hotspot area was introduced to divide the monitoring area, and then in clustering stage, the amount of data outside the hotspot area was reduced by using uneven clustering algorithm which could integrate data within the clusters. Secondly, energy consumption was cut down in the hotspot area during clustering stage by no clustering. Finally, in inter-cluster communication phase, the Particle Swarm Optimization (PSO) algorithm was addressed to seek optimal transmission path which could simultaneously meet the minimization of the maximum next hop distance between two nodes in the routing path and the minimization of the maximum hop count, so the minimization of whole network energy consumption was realized. Theoretical analysis and experimental results show that, compared with the Reinforcement-Learning-based Lifetime Optimal routing protocol (RLLO) and Multi-Layer routing protocol through Fuzzy logic based Clustering mechanism (MLFC) algorithm, the proposed algorithm shows better performance in energy efficiency and energy consumption uniformity, and the network lifetime is raised by 20.1% and 40.5%, which can avoid the "energy hole" effectively.
Due to the threats of Cross-Site Scripting (XSS) attack in Online Social Network (OSN), a approach combined classifiers and improved n-gram model was proposed to detect the malicious OSN webpages infected with XSS code. Firstly, similarity-based features and difference-based features were extracted to build classifiers and the improved n-gram model. After that, the classifiers and model were combined to detect malicious webpages in OSN. The experimental results show that compared with the traditional classifier detection methods, the proposed approach is more effective and the false positive rate is about 5%.
According to the IEEE 802.15.4 slotted Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) algorithm, a network analysis model using analysis method of two-dimensional Markov chain was proposed. Not only the sleep mode of IEEE 802.15.4 agreement but also the condition where the backoff window reached the maximum value before the Number of Backoff (NB) were especially considered in the model. On this basis, combined with M/G/1/K queuing theory, the throughput expression was derived, and the packet arrival rate effect on the throughput was analyzed under unsaturated network. Using the simulation platform Network Simulator Version2 (NS2), the experimental results show that the theoretical analysis fits well with the simulation result, and the network throughput is described accurately. Then the effectiveness of the analytical model is validated.