Authenticated encryption schemes with message linkages for message flows

Two efficient authenticated encryption schemes with message linkages are proposed. One is a basic scheme, that it has the better performance in comparison with the all previously proposed schemes in terms of the communication and the computation costs. However, it has a property as same as the previously proposed schemes, that the message blocks can be recovered only after the entire signature blocks have been received. Therefore, the basic scheme is applicable to encrypt all-or-nothing flow. Thus, we improve the basic scheme and also propose a generalized scheme, which allows the receiver to recover the partial message blocks before receiving the entire signature blocks. That is, the receiver may perform the receiving and the recovering processes simultaneously. Therefore, the generalized scheme is applicable to message flows. The generalized scheme requires smaller bandwidth and computational time as compared to the previously proposed authenticated encryption schemes with message linkages for message flows.     

Improvements of authenticated encryption schemes with message linkages for message flows

Recently, Tseng et al. proposed two authenticated encryption schemes (basic scheme and generalized scheme) with message linkages, which are efficient in terms of the communication and computation costs in comparison with all the previously proposed schemes. The basic authenticated encryption scheme suited for only after receiving the entire signature blocks, the recipient can then recover the message blocks. In order to allow the receiver to perform the receiving and the recovering processes simultaneously according to application requirements and the transmission efficiency of the network, the generalized authenticated encryption scheme was then proposed. In this paper, we show that both Tseng et al.’s authenticated encryption schemes do not achieve integrity and authentication. Improvements are then proposed to repair the weaknesses.     

Hiding message delivery latency using Direct-to-Cache-Transfer techniques in message passing environments

Communication overhead is the key obstacle to reaching hardware performance limits. The majority is associated with software overhead, a significant portion of which is attributed to message copying. To reduce this copying overhead, we have devised techniques that do not require to copy a received message in order for it to be bound to its final destination. Rather, a late-binding mechanism, which involves address translation and a dedicated cache, facilitates fast access to received messages by the consuming process/thread.We have introduced two policies namely Direct to Cache Transfer (DTCT) and lazy DTCT that determine whether a message after it is bound needs to be transferred into the data cache. We have studied the proposed methods in simulation and have shown their effectiveness in reducing access times to message payloads by the consuming process.     

Compositional message sequence charts

A message sequence chart (MSC) is a standard notation for describing the interaction between communicating objects. It is popular among the designers of communication protocols. MSCs enjoy both a visual and a textual representation. High-level MSCs (HMSCs) allow specifying infinite scenarios and different choices. Specifically, an HMSC consists of a graph, where each node is a finite MSC with matched send and receive events, and vice versa. In this paper we demonstrate a weakness of HMSCs, which disallows one to model certain interactions. We will show, by means of an example, that some simple finite state communication protocol cannot be represented using HMSCs. We then propose an extension to the MSC standard which allows HMSC nodes to include unmatched messages. The corresponding graph notation will be called HCMSC, which stands for high-level Compositional message sequence charts. With the extended framework, we provide an algorithm for automatically constructing an MSC representation for finite state asynchronous message passing protocols.     

Scaffolding collaborative argumentation in asynchronous discussions with message constraints and message labels

This study examined the effects of message constraints and labels on collaborative argumentation in asynchronous online discussions. Thirty-eight undergraduate students in an introductory educational technology course were assigned to one of three groups. In one group, students posted specific types of messages using a prescribed set of message categories such as argument, evidence, critique, and explanation. Using the same message categories, another group inserted message labels directly into the subject headings to identify each message by category and increase the visibility of the arguments and challenges presented in debates. A control group received none of the above instructions and constraints. Students in the constraints-with-labels group were significantly less likely to (a) challenge other students, and (b) respond to challenges from other students. The label used to identify critiques might have discouraged students from posting critiques and shifted attention to posting more arguments, following up explanations with more explanations, and evidence with more evidence.     

带有附件的SOAP消息及实现

为了在服务之间传输图像、语音等二进制文件,需要在SOAP消息中加入附件与SOAP消息一同传输。分析了SOAP协议,论述了SOAP协议的体系结构、特点。对带附件的SOAP消息格式、附件的引用方法以及相应SOAP处理器的处理规则进行了详细论述,叙述了如何利用SOAP和MIME自身的功能把附件与SOAP消息捆绑传输,并用Apache SOAP给出处理附件的方法。     

Meteorological satellites

Abstract

The first meteorological satellite was placed in orbit in 1960. The European programme began in earnest in 1977 with the launch of a geostationary satellite, Meteosat-1. This paper provides a brief history of the development of the Meteosat programme and describes the operational services which are provided including the range of meteorological products which are extracted routinely from the satellite data at the European Space Operations Centre (ESOC).     

Approximate image message authentication codes

This paper introduces approximate image message authentication codes (IMACs) for soft image authentication. The proposed approximate IMAC survives small to moderate image compression and it is capable of detecting and locating tampering. Techniques such as block averaging and smoothing, parallel approximate message authentication code (AMAC) computation, and image histogram enhancement are used in the construction of the approximate IMAC. The performance of the approximate IMAC in three image modification scenarios, namely, JPEG compression, deliberate image tampering, and additive Gaussian noise, is studied and compared. Simulation results are presented     

The message is the medium

We are exploring the use of visual imagery which simultaneously provides the content and control of web-based interactive services. We describe four unconventional web-based services we have implemented for: messaging, a bulletin board, broadcast messages, and browsing through a set of hyperlinked objects. We implement each service using a real-world metaphor which serves as the basis for the visual presentation as well as the service itself; thus form and function are tightly coupled. The use of universal imagery eliminates the need for wordy explanations and hence increases accessibility to an international audience. During the course of development, we devised techniques to enhance the shared experiences of the visitors to our sites, including automatically generated 2D animations. These approaches can be applied to a variety of web-sites and are also described.     

适应性阈值优化的微博消息索引模式

为提高微博搜索的准确性,提出一种适应性的微博消息索引模式。将微博消息的转发和回复表示为树形结构并进行编码;提出一种基于内容和排名的索引模式,根据新消息的到来适应性地调整内存中的索引数据;为避免检索过程扫描整个微博数据集,提出一种Top-k阈值优化方法。Twitter数据实验结果表明,该模式降低了微博数据索引时的时间和空间开销,其性能随着时间的推移比较稳定。     

短信过滤系统设计分析*

设计了一种手机终端上基于短信内容的垃圾短信过滤系统。系统采用了平衡Winnow算法,该算法具有分类速度快、性能好以及支持在线更新的优点,适用于手机终端资源有限、需要实时或者定期更新分类器的情况。通过一系列的实验分析,证明该方法的有效性,并给出了对该方法的全面评估。对于该算法将来在信息过滤领域的应用,提供了全面的分析依据。     

Non-blocking message total ordering protocol

Message total ordering is a critical part in active replication in order to maintain consistency among members in a fault tolerant group. The paper proposes a non-blocking message total ordering protocol （NBTOP） for distributed systems. Non-blocking property refers to that the members in a fault tolerant group keep on running independently without waiting for installing the same group view when a fault tolerant group evolves even when decision messages collide. NBTOP takes advantage of token ring as its logical control way. Members adopt re-requesting mechanism （RR） to obtain their lost decisions. Forward acknowledgement mechanism （FA） is put forth to solve decision collisions. The paper further proves that NBTOP satisfies the properties of total order, agreement, and termination. NBTOP is implemented, and its performance test is done. Comparing with the performance of Totem, the results show that NBTOP has a better total ordering delay. It manifests that non-blocking property helps to improve protocol efficiency.