Distributed Timestamp Mechanism Based on Verifiable Delay Functions

In the data communication system,the real-time information interaction of communication device increases the risk of privacy sensitive data being tam-pered with.Therefore,maintaining data security is one of the most important issues in network data communication.Because the timestamp is the most impor-tant way to authenticate data in information interaction,it is very necessary to pro-vide timestamp service in the data communication system.However,the existing centralized timestamp mechanism is difficult to provide credible timestamp ser-vice,and users can conspire with timestamping servers to forge timestamps.Therefore,this paper designs a distributed timestamp mechanism based on contin-uous verifiable delay functions.It utilizes multiple independent timestamp servers to provide timestamp services in a distributed model and appends the timestamp to the data once the data is generated.Thus,it can prove that the data already exists at a certain time and ensure the accuracy of the timestamp.Moreover,a digital blind signature based on elliptic curve cryptography is utilized to solve the problem of timestamp forgery in timestamp service.Finally,the security ana-lysis of the scheme ensures the data security of data communication system and the concurrency rate of timestamp.The experimental results also show that the scheme greatly improves the efficiency of digital signatures.

Distributed Timestamp Synchronization for End Hopping

End hopping is an active and effective technology for defending against adversaries in the network warfare.Synchronization is a key technology of end hopping.However,the common synchronization methods are insufficient for end hopping.Based on timestamp synchronization,this paper proposes a novel method of Distributed Timestamp Synchronization(DTS)to improve the capacity of synchronization.DTS uses a list of timestamp servers which are located all over the Internet to synchronize timestamp,and a list of clock offsets to adjust the synchronized timestamp.DTS can overcome the main deficiencies(request overwhelming and boundary failure)of timestamp synchronization.Experiments show that DTS is a feasible synchronization technology for end hopping.

Precise measurement method of optical fiber length based on timestamp technique

A measurement method of optical fiber length using timestamp technique is demonstrated. Based on IEEE1588 precise clock synchronization protocol, the principle that time delay asymmetry on two path results in synchronization time deviation is used, and the difference between two-path delays could be deduced by measuring the synchronization time deviation reversely. Then the length of optical fiber on one path could be calculated if that on the other path is known Due to the fact that the path of Sync and Delay_Req message is symmetric, the optical pulse dispersion and the asymmetry of photoelectric detector performance on two paths are averaged by exchanging two optical fibers. The time difference between master and slave clocks is eliminated by sharing the same time base. At last, the lengths of two single-mode optical fibers are measured with the uncertainty of 0. 578 m for 3 227. 722 m and 0. 758 m for 25 491. 522 m, respectively. Thus this method has high precision and long range.

An Improved Biometric Fuzzy Signature with Timestamp of Blockchain Technology for Electrical Equipment Maintenance

The power infrastructure of the power system is massive in size and dispersed throughout the system.Therefore,how to protect the information security in the operation and maintenance of power equipment is a difficult problem.This paper proposes an improved time-stamped blockchain technology biometric fuzzy feature for electrical equipment maintenance.Compared with previous blockchain transactions,the time-stamped fuzzy biometric signature proposed in this paper overcomes the difficulty that the key is easy to be stolen by hackers and can protect the security of information during operation and maintenance.Finally,the effectiveness of the proposed method is verified by experiments.

Classification and quantification of timestamp data quality issues and its impact on data quality outcome

Timestamps play a key role in process mining because it determines the chronology of which events occurred and subsequently how they are ordered in process modelling.The timestamp in process mining gives an insight on process performance,conformance,and modelling.This therefore means problems with the timestamp will result in misrepresentations of the mined process.A few articles have been published on the quantification of data quality problems but just one of the articles at the time of this paper is based on the quantification of timestamp quality problems.This article evaluates the quality of timestamps in event log across two axes using eleven quality dimensions and four levels of potential data quality problems.The eleven data quality dimensions were obtained by doing a thorough literature review of more than fifty process mining articles which focus on quality dimensions.This evaluation resulted in twelve data quality quantification metrics and the metrics were applied to the MIMIC-ll dataset as an illustration.The outcome of the timestamp quality quantification using the proposed typology enabled the user to appreciate the quality of the event log and thus makes it possible to evaluate the risk of carrying out specific data cleaning measures to improve the process mining outcome.

Digital signal acquisition system for complex nuclear reaction experiments

A digital data-acquisition system based on XIA LLC products was used in a complex nuclear reaction experiment using radioactive ion beams.A flexible trigger system based on a field-programmable gate array(FPGA)parametrization was developed to adapt to different experimental sizes.A user-friendly interface was implemented,which allows converting script language expressions into FPGA internal control parameters.The proposed digital system can be combined with a conventional analog data acquisition system to provide more flexibility.The performance of the combined system was veri-fied using experimental data.

Factors affecting forensic electric network frequency matching-A comprehensive study

The power system frequency fluctuations could be captured by digital recordings and extracted to compare with a reference database for forensic timestamp verification.It is known as the Electric Network Frequency(ENF)criterion,enabled by the properties of random fluctuations and intra-grid consistency.In essence,this is a task of matching a short random sequence within a long reference,whose accuracy is mainly concerned with whether this match could be uniquely correct.In this paper,we comprehensively analyze the factors affecting the reliability of ENF matching,including the length of test recording,length of reference,temporal resolution,and Signal-to-Noise Ratio(SNR).For synthetic analysis,we incorporate the first-order AutoRegressive(AR)ENF model and propose an efficient Time-Frequency Domain noisy ENF synthesis method.Then,the reliability analysis schemes for both synthetic and real-world data are respectively proposed.Through a comprehensive study,we quantitatively reveal that while the SNR is an important external factor to determine whether timestamp verification is viable,the length of test recording is the most important inherent factor,followed by the length of reference.However,the temporal resolution has little impact on performance.Finally,a practical workflow of the ENF-based audio timestamp verification system is proposed,incorporating the discovered results.

基于数据流传播路径学习的智能合约时间戳漏洞检测

智能合约是一种被大量部署在区块链上的去中心化的应用.由于其具有经济属性,智能合约漏洞会造成潜在的巨大经济和财产损失,并破坏以太坊的稳定生态.因此,智能合约的漏洞检测具有十分重要的意义.当前主流的智能合约漏洞检测方法(诸如Oyente和Securify)采用基于人工设计的启发式算法,在不同应用场景下的复用性较弱且耗时高,准确率也不高.为了提升漏洞检测效果,针对智能合约的时间戳漏洞,提出基于数据流传播路径学习的智能合约漏洞检测方法Scruple.所提方法首先获取时间戳漏洞的潜在的数据传播路径,然后对其进行裁剪并利用融入图结构的预训练模型对传播路径进行学习,最后对智能合约是否具有时间戳漏洞进行检测.相比而言,Scruple具有更强的漏洞捕捉能力和泛化能力,传播路径学习的针对性强,避免了对程序整体依赖图学习时造成的层次太深而无法聚焦漏洞的问题.为了验证Scruple的有效性,在真实智能合约的数据集上,开展Scruple方法与13种主流智能合约漏洞检测方法的对比实验.实验结果表明,Scruple在检测时间戳漏洞上的准确率,召回率和F1值分别可以达到0.96,0.90和0.93,与13种当前主流方法相比,平均相对提升59%,46%和57%,从而大幅提升时间戳漏洞的检测能力.

多头注意力机制的图同构网络智能合约源码漏洞检测

针对智能合约源码转化为字节码后部分语法、语义丢失,且现有漏洞检测方法精度低、误报率高,特别是对重入漏洞和时间戳漏洞的检测能力有限等问题,提出一种多头注意力机制的图同构网络智能合约源码漏洞检测方法。使用智能合约源码,结合重入漏洞和时间戳漏洞特点构建图结构并将其规范化;将规范化后的图结构数据投入图同构网络进行迭代训练,利用该网络强大的节点表示和图表示能力进行漏洞检测;在图同构网络的基础上增加多头注意力机制,进一步增强图同构网络的节点表示能力。实验结果显示该方法对重入漏洞和时间戳漏洞检测准确率达到93.08%和92.30%,相较于普通图同构网络方法分别提升1.44和2.00个百分点。证明该方法对相关漏洞的检测能力要优于其他检测工具。

基于时间戳的异质信息网络数据动态加密传输

针对异质信息网络动态数据特征种类多、数据量大,在数据传输过程中易出现安全隐患等问题,提出一种基于时间戳的加密传输算法。采用DES算法建立网络数据加密种类查询表,标记关键字词字符,通过逆转换初始数据关键词的IP位置,计算得到关键词所处位置的属性、状态以及频率等信息,按照信息参数给出对应加密密钥。在此基础上,定义异质信息网络无向图,采用时间戳算法描述网络实时动态特性,划分网络中静态数据与动态数据,建立混淆矩阵,按照节点跟随时间的游走变化关系构建加密传输序列,完成最终数据加密传输。实验结果证明,所提算法的加密效果好,对任何类型的网络数据均能实现高效加密,且数据传输完整性较高。

基于特征调制图神经网络的智能合约源码漏洞检测

随着区块链技术的广泛应用,智能合约的安全问题引起广泛关注。针对智能合约源码向字节码转化会丢失部分语义信息,而现有深度学习漏洞检测方法不能很好地检测重入漏洞和时间戳漏洞等问题,本文提出一种基于特征调制图神经网络的智能合约源码漏洞检测方法(GNN-film)。首先,分析重入漏洞和时间戳漏洞的特点,使用智能合约源码构建图结构并将其精简化;其次,搭建基于特征级线性调制的图神经网络模型,利用该网络模型强大的特征调制能力对合约漏洞特征进行精确表示;最后,将精简化后的图结构数据输入搭建的模型中获得检测结果。实验结果显示,本文方法对重入漏洞和时间戳漏洞检测的准确率达到91.00%和91.64%,相较基于图神经网络的方法分别提升了4.20百分点和9.70百分点,证明本文方法对相关漏洞检测的能力要优于其他检测工具。

基于时间戳间距的用户在线时长聚类方法

在网络用户行为分析中,以时序维度为基础,研究用户网络行为的变化趋势,提出并挖掘更多有价值的信息,可为管理或商业决策提供有力支持。为此,文中提出一种基于时间戳间距的用户在线时长聚类方法,以用户访问日志文件中时间戳之间的间距作为特征,首先将获取的日志数据进行预处理,获得用户的在线时长统计;然后采用K-Means聚类算法对用户进行聚类,并使用轮廓系数对K值进行评价分析,确定聚类K值范围,准确判定用户单次访问在线时长及类型。采用真实校园网用户访问日志数据对所提方法进行评价,实验结果表明,该方法的准确度达到0.9180,精确度达到0.7685,召回率达到0.8093。

带有时间戳的着色逻辑Petri网

针对扩展着色逻辑Petri网存在的表达能力弱以及适用范围窄的问题,提出了一个新的Petri网模型,即带有时间戳的着色逻辑Petri网。首先,将颜色进行实例化以及将变量用于构建有向边上的表达式使得模型能够传递复杂的数据流。其次,引入全局时间以及令牌的时间戳等概念为变迁使能规则增加时间上的约束,使得模型能够用于模拟实时系统。再次,定义库所约束函数并为变迁使能规则增加输出库所上的约束,使得模型能够适用于存储资源有限的场景。接着,提出基于逻辑变迁输入输出矩阵的匹配法,降低逻辑输入变迁的使能判定计算开销并简化逻辑输出变迁的使能判定计算过程。然后,重新定义适用于三类变迁的使能判定条件以及适用于三类库所的标记更新方法,解决原有模型语义在新模型中不适用的问题。最后,通过实例说明新的Petri网模型具有更强的表达能力和适用范围,它能够适用于传递复杂数据流、存储资源有限、实时的且包含批处理选择结构的系统。

许可链下的事务并行执行模型

现有的许可链系统大多采取串行的事务执行方式,无法利用多核处理器的性能优势。在共识算法性能较高的许可链中,这种串行的事务执行方法将会成为性能瓶颈。为降低排序-执行-验证架构的许可链中事务执行的时间开销,文中提出了两种事务并发模型。首先,提出了基于地址表的并行执行模型,通过静态分析的方法将事务的读写集映射到地址表中,并利用地址表构建调度图实现无数据冲突的事务并行执行;其次,针对静态分析方法不适用于读写需求复杂的应用场景,提出了基于多版本时间戳排序的并行执行模型,领导者节点使用多版本时间戳排序算法并行地预执行事务并将调度图以事务依赖三元组的形式存储入区块,所有验证节点通过事务依赖三元组进行调度,在保证一致性的前提下实现事务的并行执行;最后,在Tendermint中实现了所设计的两种事务并发模型,并进行了事务执行阶段性能测试和多节点性能测试。实验结果表明,相比串行执行,所提模型在单节点8线程时的事务执行时间分别减少了68.6%和28.5%,4节点8线程时区块链吞吐量分别提升了约43.4%和19.5%。

基于时间戳特征提取和CatBoost-LSTM模型的光伏短期发电功率预测

为解决预测模型输入特征维度不足以及单一模型预测精度不高而导致的短期功率预测效果较差的问题,提出一种对时间戳进行特征提取(FE)的CatBoost和长短期记忆(LSTM)神经网络组合的光伏短期发电功率预测模型。首先,利用信息熵加权的方式对传统灰色关联分析进行改进,并采用改进方法对辐照度、温度、降雨量等气象特征与发电功率特征进行关联性分析,选择关键特征作为输入特征;然后,从时间戳和功率特征中提取年、月、日、时、分、秒、时间戳-功率等新时序特征;在此基础上,将关键气象特征与提取的新时序特征用于组合模型训练;最后,利用光伏电站的真实运行数据对所提方法和组合模型进行算例分析。结果表明:提取的新时序特征和组合模型均有助于提高预测精度,在非晴天工况下组合模型的预测误差较单一模型可降低12~23个百分点,且与其他组合模型相比具有更高的预测精度。

一种TSN交换机的时钟同步系统设计

时间敏感网络以其确定性、低抖动、高可靠等特征,保障了网络传输的实时性需求,是目前国际产业界正在积极推动的全新工业通信技术。基于研究时间敏感网络技术解决方案的目的,采用硬件时间戳、LinuxPTP软件包和设置AS开关的方法,提出一种时间敏感交换机的时钟同步实现机制,同时,结合验证同步精度和标准符合度的实验,检验了该机制的准确性。结果表明,单跳同步精度在30 ns以内,同步过程符合协议要求。对时间敏感网络在工业互联网、汽车电子、远程医疗等行业的应用有一定的参考价值。

基于医院信息系统时间戳的区块链电子认证应用与实现

随着智慧医疗信息化的快速发展,确保医院信息系统数据的真实性和完整性成为亟待解决的问题。本文设计实现了基于医院信息系统时间戳的电子认证应用,引入区块链技术,实现了医疗数据的可靠认证和可追溯性,解析医院信息系统时间戳和区块链技术的基本原理,详细阐明了时间戳可避免并发情况,确保链上医疗按照先后发生的顺序。此项应用使得医疗数据更加稳定可靠,为相关应用场景提供坚实的基础,对开发高效、安全的医疗数据认证方法具有重要意义。

视频信号同步传输技术在广播电视视频摄像中的应用

视频信号同步传输技术在广播电视视频摄像领域发挥着至关重要的作用,通过精确的时间戳和同步信号,确保多路视频信号在采集、传输和制作过程中的精确同步,是实现高质量、低延迟视频传输与制作的关键。详细阐述视频信号同步传输技术在高清视频传输与分发、实时直播与远程制作、多摄像机拍摄与剪辑等方面的具体应用,通过案例分析,展示该技术在复杂转播制作环境下的优越性能。

“百城千屏随身听”业务的技术挑战与实现

中央广播电视总台“百城千屏随身听”业务通过“百城千屏”超高清视音频传播系统使用异构网络额外传输一路节目伴音,在大屏侧实现大屏视频与移动终端上的节目伴音同步呈现。本文阐述了该业务面临的技术挑战和对应的实现方式。

Timestamp reassignment:taming transaction abort for serializable snapshot isolation

Serializable snapshot isolation(SSI)is a promising technique to exploit parallelism for multi-core databases.However,SSI suffers from excessive transaction aborts.Existing remedies have three drawbacks:1)tracking prohibitively transitive dependencies;2)aborting on every writewrite conflict;and 3)requiring manual annotation on transaction programs.In this paper,we propose to suppress transaction aborts by reassigning timestamps.We combine static analysis with augmented query plan.In this way,we save both aborts caused by read-write and write-write conflicts,without tracking transitive dependency and annotating transaction programs.As such,our approach does not exhibit drawbacks of existing methods.Extensive experiments demonstrate the effectiveness and practicality of our approach.