基于信用等级划分的医疗数据安全共识算法

在基于区块链的医疗数据共享系统中为防御恶意节点攻击并且提高共识效率,该文提出基于信用等级划分的医疗数据安全共识算法(SCA_MD).首先,在SCA_MD中,考虑由数据节点、共识节点和监管节点组成的医疗区块共识模型,提出相应的节点身份验证机制,实现快速验证.其次,提出基于海洋掠食者的自我优化信用等级划分算法(SCRD),...     

面向车联网异构节点的区块链高效一致性共识算法研究

车联网异构节点由于其性能差异大、具有移动性等原因会造成区块链共识算法交易吞吐率低、交易时延较大等问题,该文提出面向车联网异构节点的区块链高效一致性共识算法(ECCA).首先,在ECCA中,考虑由验证节点、一般节点和恶意节点组成的车联网异构节点,提出一种信用等级机制,实现信用等级划分和3类异构节点的划分.其次,提出一种跨...     

Recent advances in consensus protocols for blockchain: a survey

Wireless Networks - As the core of a blockchain system, the consensus mechanism not only helps to maintain the consistency of node data, but also gets involved in the issuance of tokens and...     

Voting mechanisms in distributed systems

It is shown how voting mechanisms can be exploited to improve the reliability of decisions in a distributed system. A model of decision making in which several processors (nodes) are assigned to work independently on various aspects of a problem and each returns a binary answer to a coordinator node is assumed. The coordinator combines the answers, using a voting mechanism to arrive at a final answer. Two issues are addressed: (1) if the reliability of each node is known, then by assigning suitable votes to the various nodes it is possible to maximize the probability of a correct decision by the coordinator; and (2) if a cost vs. reliability function for each node is known, then it is possible to determine a best operating point for each node so as to minimize the total cost of the computation. Algorithms for minimizing the cost were designed and tested, and conditions under which savings can be realized were identified     

Weighted voting on the blockchain: Improving consensus in proof of stake protocols

Proof of stake (PoS) protocols rely on voting mechanisms to reach consensus on the current state. If an enhanced majority of staking nodes, also called validators, agree on a proposed block, then this block is appended to the blockchain. Yet these protocols remain vulnerable to faults caused by validators who abstain either accidentally or maliciously. To protect against such faults while retaining the PoS selection and reward allocation schemes, we study weighted voting in validator committees. We formalize the block creation process and introduce validators' voting profiles which we update by a multiplicative weights algorithm relative to validators' voting behavior and aggregate blockchain rewards. Using this framework, we leverage weighted majority voting rules that optimize collective decision making to show, both numerically and analytically, that the consensus mechanism is more robust if validators' votes are appropriately scaled. We raise potential issues and limitations of weighted voting in trustless, decentralized networks and relate our results to the design of current PoS protocols.     

ZBFR: zone based failure recovery in WSNs by utilizing mobility and coverage overlapping

Wireless sensor networks are more prone to failures as compared to other traditional networks. The frequent faults and failures sometime create large holes causing loss of sensing and connectivity coverage in the network. In present work, a zone based failure detection and recovery scheme is presented to reliably handle such node failures. We first propose a consensus and agreement based approach to elect a suitable monitor node called as zone monitor (ZM). ZM is responsible for coordinating failure recovery activities and maintaining desired coverage within a zone. In order to overcome failure overhead due to false failure detection, a consensus is carried out amongst neighboring nodes of a suspicious node to confirm the correct status with high accuracy. On confirmation of a node failure, the impact of resulting hole on coverage is analyzed and if impact exceeds beyond a particular threshold, a recovery process is initiated. The recovery process utilizes backup nodes having overlapping sensing coverage with failed node and may also relocate some nodes. Firstly a backup node is probed and activated if available. If no backup node is found, the solution strives to recover coverage jointly by recursively relocating some mobile nodes and probing backup nodes. The proposed scheme is analyzed and validated through NS-2 based simulation experiments.     

Performance optimization for smart grid blockchainintegrated with fog computing using DDQN

In order to solve the energy crisis and pollution problems, smart grid is widely used. However, there are many challenges such as the management of distributed energy during the construction. Blockchain, as an emerging technology, can provide a secure and transparent solution to the decentralized network. Meanwhile, fog computing network is considered to avoid the high deployment cost. The edge servers have abundant computing and storage resources to perform as nodes in grid blockchain. In this paper, an innovative structure of smart grid blockchain integrated with fog computing are proposed. And a new consensus mechanism called scalable proof of cryptographic selection (SPoCS) is designed to adapt the hybrid networks. The mechanism not only includes a special index, contribution degree, to measure the loyalty of fog nodes and the probability of being a function node, but also has flexible block interval adjustment method. Meanwhile, the number of function nodes (validating nodes and ordering nodes) can also be adjusted. And a deep reinforcement learning (DRL) method is used to select the appropriate quantity to improve the performance under the strict constraints of security and decentralization. The simulation shows the scheme performs well in the throughput, cost and latency.     

无线传感器网络节点复制攻击和女巫攻击防御机制研究

在无线传感器网络(WSNs)中,节点复制攻击和女巫攻击可扰乱数据融合和阈值选举等网络操作.发起这两种攻击需先通过邻居发现认证过程.考虑到在WSNs中发起邻居认证是不频繁的,提出了一种基于单向密钥链的ID认证防御机制(OKCIDA),降低攻击者在任何时间段发起这两种攻击的可能性.然后基于椭圆曲线离散对数问题,构造对称参数,并组合OKCIDA和利用节点邻居关系,提出了一种无需位置的邻居认证协议(LFNA),以阻止复制节点和女巫节点成功加入网络.最后给出了安全性证明和分析,并在安全和开销方面将LFNA与已有典型防御方案进行了比较,结果表明该方案具有一定的优势.     

6G oriented blockchain based Internet of things data sharing and storage mechanism

Considering the heterogeneity of various IoT system and the single point failure of centralized data-processing platform,a decentralized IoT data sharing and storage method based on blockchain technology was proposed.The block consensus and decentralized storage of shared data were realized through the PoS consensus mechanism.A block layered propagation mechanism between consensus node and verified node was proposed based on the Gossip protocol.The block propagation delay model and decentralization evaluation model of blockchain networks were derived.The trade-off between the block propagation delay and the decentralization degree of networks was analyzed.The simulation results demonstrate that the block propagation delay and degree of network decentralization decrease with the increase of minimal capabilities of consensus nodes.As an application example,in the trajectory data sharing scenario of confirmed patients,the data sharing smart contract is implemented and tested based on the Ethereum development platform.     

Primary User Emulation Detection Algorithm Based on Distributed Sensor Networks

In this paper, we propose a novel primary user emulation (PUE) detection approach which employs a distributed sensor network, where each sensor node operates as an independent PUE detector. Distributed nodes collaborate in order to obtain the final detection results for the whole network. A voting algorithm is used to improve the performance of energy detection, while the classification is conducted by the nearest node in order to improve the efficiency of the detector. As a result of voting, if a potential primary user exists, then the features of the unknown user is compared with entries from the database in order to obtain a solid detection match. An artificial neural network (ANN) is used for the classification of an unknown user. To assess the accuracy of the detection result, we implement a reliability check at the output of ANN. The proposed algorithm is validated via computer simulations as well as by experimental hardware implementations using the Universal Software Radio Peripheral (USRP) software-defined radio (SDR) platform. The experiment results show that the distributed network detector detects the PUE 180–200%, depending on the number of primary users, faster than single node detector.     

Co-operation Enforcing Reputation-Based Detection Techniques and Frameworks for Handling Selfish Node Behaviour in MANETs: A Review

In Mobile Ad hoc Network, co-operation between mobile nodes is inevitable for enabling reliable network connectivity due to the absence of pre-deployed infrastructure. In such a network, mobile nodes spend significant amount of energy for detecting routes and forwarding packets in order to enforce co-operation. The energy drain of mobile nodes due to the above fact induces them to refuse forwarding of packets for their neighbouring nodes in order to participate in the network. The mobile nodes that forward their own packets but drop the packets received from neighbours are known as selfish nodes. Detecting selfish nodes is one of the most challenging issues that need to be addressed for enforcing co-operation. The core objective of this research work is to essentially identify and highlights various reputation-based selfish node mitigation approaches available in the literature with their merits and limitations. This paper presents context-aware reputation-based selfish node mitigation approaches that are classified into three categories viz., History-based reputation mechanism, Condition probability-based reputation mechanism and Futuristic probability-based reputation mechanism. This paper further presents a review on a number of selfish node mitigation frameworks and also aims in emphasizing the role of statistical reliability co-efficient that could aid in effective and efficient mitigation of selfish nodes.     

一种基于LEACH改进的均匀分簇路由算法

针对LEACH分簇算法簇头分布位置不均匀以及节点耗能不均衡等缺点,该文提出一种双SINK节点均匀分簇算法DSUC。该算法首先利用无信标节点ABC定位算法,计算出每个节点的坐标位置,再根据理论得出的最佳簇头数将整个无线网络区域尽可能地划分成均等的区域,然后SINK节点通过各节点坐标选举各区域内离质心最近的节点做为第一轮簇头节点。在区域的对称位置上设置两个SINK节点,轮流交替工作,能有效的解决“热区”问题。     

On the design of node architectures and MAC protocols for optical burst-switched ring networks

Efficient multiple-token-based MAC protocols have been proposed for optical burst-switched (OBS) unidirectional ring networks using a TT-TR-based node architecture in our previous research. However, the unidirectional OBS ring network is difficult to scale to larger networks. As wavelengths accessibilities are dominated by tokens, network performance is restricted by the frequency of capturing a token. If the network is too large, it takes a long time for tokens to rotate. Thus, a destination queue may wait for a long time to be served, which results in large queuing delays and inefficiency of network resource utilization. In order to improve network efficiency and scalability for OBS ring networks using multiple tokens, this work is extended to a bidirectional ring system that uses the tunable transmitter and tunable receiver (TT-TR)-based node architecture with two pairs of transceivers, so that each queue can be served by tokens from both directions. Furthermore, two kinds of node architectures differing in sharing the two pairs of transceivers, either shared or not, are proposed. Then, two MAC protocols considering different queue scheduling algorithms are proposed for the ring network using the proposed node architectures, in order to use the network resources more efficiently. They are improved from general round-robin (GRR) and termed as half-ring round-robin (HfRR) and co-work round-robin (CoRR), respectively. The network performance of the two proposed node architectures and the two proposed MAC protocols for the networks using them as well as the network scalability are evaluated with the OPNET simulator.     

Asynchronous failed sensor node detection method for sensor networks

Detecting failed nodes is important in a sensor network, because a failed node can cause coverage and connectivity holes. Since sensors are resource‐limited devices, lack of a clocking mechanism imposes difficulties in implementing synchronous failure detection techniques. To counter this, asynchronous methods are needed for detecting failed sensor nodes. For example, in traditional distributed systems sent data packets and received acknowledgements are matched to identify any malfunctions. A similar approach can be adopted in sensor networks. An asynchronous failed sensor node detection (AFSD) method is proposed, where a numeric counter variable is used to track the received and sent data packets between active nodes. This variable acts as bounded for an active sensor node and unbounded for an out‐of‐communication or failed node. By observing the value of the counter, a decision can be made on a deployed sensor node. Whenever the counter value of a neighbour crosses a predefined threshold, that neighbour is suspected. However, measuring a counter value can always lead to a false positive. To avoid false suspicion, a consensus protocol is needed. Such a technique is described, which is proved as accurate and complete. The complexity analysis shows that the control, energy, and time overheads of the proposed method are linear and in the order of number of neighbours per node. Copyright © 2011 John Wiley & Sons, Ltd.     

Census: fast,scalable and robust data aggregation in MANETs

This paper describes Census, a protocol for data aggregation and statistical counting in MANETs. Census operates by circulating a set of tokens in the network using biased random walks such that each node is visited by at least one token. The protocol is structure-free so as to avoid high messaging overhead for maintaining structure in the presence of node mobility. It biases the random walks of tokens so as to achieve fast cover time; the bias involves short albeit multi-hop gradients that guide the tokens towards hitherto unvisited nodes. Census thus achieves a cover time of O(N) and message overhead of \(O(N\,log(N))\) where N is the number of nodes. Notably, it enjoys scalability and robustness, which we demonstrate via simulations in networks ranging from 100 to 4000 nodes under different network densities and mobility models. We also observe a speedup by a factor of k when k different tokens are used (\(1 \le k \le \sqrt{N}\)).     

Stimulating Cooperation in Self-Organizing Mobile Ad Hoc Networks

In military and rescue applications of mobile ad hoc networks, all the nodes belong to the same authority; therefore, they are motivated to cooperate in order to support the basic functions of the network. In this paper, we consider the case when each node is its own authority and tries to maximize the benefits it gets from the network. More precisely, we assume that the nodes are not willing to forward packets for the benefit of other nodes. This problem may arise in civilian applications of mobile ad hoc networks. In order to stimulate the nodes for packet forwarding, we propose a simple mechanism based on a counter in each node. We study the behavior of the proposed mechanism analytically and by means of simulations, and detail the way in which it could be protected against misuse.     

Design and performance comparison of multiple-token based MAC protocols for optical burst switched ring networks

Optical burst switching (OBS) has been proposed as a new optical switching paradigm for the next generation Internet due to its flexibility and feasibility compared to OCS and OPS. Moreover, serving as a backbone that interconnects a number of access networks, OBS ring topologies have been a good choice for solving the current metro gap problem between core network and access network owning to its simplicity and scalability. In this paper, we provide an insight into the OBS ring network that consists of nodes using TT–TR (Tunable Transmitter–Tunable Receiver). The node architectures with TT–TR may make efficient use of network resources even though traffic pattern, such as IP traffic with self-similarity dynamically change, and can support good expandability. However, all nodes share the limited network resources. This may result in contention such as wavelength contention and transceiver contention leading to burst loss. In order to use the shared network resources fairly and efficiently as well as reducing the resource contention, we focus on the design of medium access control (MAC) protocols based on multiple tokens. Each token is allocated to one wavelength to denote the accessibility of that wavelength, i.e., once the token is captured, the corresponding wavelength can be used to transmit a burst. As tokens hold the key for using wavelengths to transmit bursts, token management including the token release time is crucial in the proposed MAC protocols. Thus, two kinds of multiple-token based MAC protocols with different token release times are proposed: token release after transmitting burst (TRTB) and token release after transmitting control header (TRTC). Each of them is classified into two schemes called TRTB/TRR and TRTB/RCA and correspondingly TRTC/TRR and TRTC/ RCA. RCA stands for receive collision avoidance. The target is to increase the performance while reducing the processing overhead at each node. The performance of the TRTB and TRTC protocols are evaluated and compared in terms of queuing delay, burst loss rate, and channel utilization by OPNET simulation. The effects of various design parameters are also investigated through simulation in order to evaluate their scalability. In all the proposed schemes, tokens are just used to denote the accessibility of each wavelength. Finally, as an alternative, we also propose a new scheme based on the TRTC protocol called TRTC/CAT (collision avoidance by tokens) to avoid contention by using tokens.

基于信任度计算的三阈值控制Ad Hoc网络节点撤销机制

为解决在资源受限且拓扑结构多变的Ad Hoc网络中对节点状态的量化控制,提出一种准确计算节点信任度值、三阈值控制的节点撤销机制.基于投诉机制的阈值用于快速将可疑节点挂起;基于信任度计算的阈值用于最终将恶意节点撤销;基于预警的阈值用于防止恶意节点短期内发起对某合法节点的连续错误投诉.分析及仿真表明:所提方案避免根据投诉数目而撤销节点的武断性,三阈值的采用保证了对潜在恶意节点的快速反应、信任度可量化及准确撤销,且能防止恶意节点对合法节点合谋投诉而造成的误撤销.     

Distributed function calculation and consensus using linear iterative strategies

Given an arbitrary network of interconnected nodes, we develop and analyze a distributed strategy that enables a subset of the nodes to calculate any given function of the node values. Our scheme utilizes a linear iteration where, at each time-step, each node updates its value to be a weighted average of its own previous value and those of its neighbors. We show that this approach can be viewed as a linear dynamical system, with dynamics that are given by the weight matrix of the linear iteration, and with outputs for each node that are captured by the set of values that are available to that node at each time-step. In connected networks with time-invariant topologies, we use observability theory to show that after running the linear iteration for a finite number of time-steps with almost any choice of weight matrix, each node obtains enough information to calculate any arbitrary function of the initial node values. The problem of distributed consensus via linear iterations, where all nodes in the network calculate the same function, is treated as a special case of our approach. In particular, our scheme allows nodes in connected networks with time-invariant topologies to reach consensus on any arbitrary function of the initial node values in a finite number of steps for almost any choice of weight matrix.     

一种基于LEACH的改进分簇路由协议

经典LEACH算法在每轮数据传输过程中,所有子节点均向汇聚节点传输数据,成员节点充当簇头次数不均匀,导致信息冗余与节点能量浪费,使网络生存时间变短。针对这一问题,提出了一种基于部分成员节点随机转发机制的分簇算法,让子节点在数据传输过程中,按照均匀分布规律,选择部分节点工作。仿真结果显示,与经典的LEACH算法相比,改进后的协议延长了约38%的网络寿命,推迟了第一节点死亡时间约13%,大大地降低了能耗。在大规模网络仿真方面,优势更明显。