The objective of this paper is to give a comprehensive introduction to applied cryptography with an engineer or computer scientist in mind. The emphasis is on the knowledge needed to create practical systems which supports integrity, confidentiality, or authenticity. Topics covered includes an introduction to the concepts in cryptography, attacks against cryptographic systems, key use and handling, random bit generation, encryption modes, and message authentication codes. Recommendations on algorithms and further reading is given in the end of the paper. This paper should make the reader able to build, understand and evaluate system descriptions and designs based on the cryptographic components described in the paper.

[서평]「Applied Cryptography」

This paper provides a concepeual framework for expressing the attributes of what constitutes dependable and reliable computing: the impairrnents to dependability: faults, errors, and failures, the means for dependability: fault-avoidance, fault-tolerance, enor-removal, and errorthe measures of dependability: reliability, availability, maintainability, and safety. Emphasis is being put on the dependability impairments and on fault-tolerance. -

Dependable computing and fault tolerance : concepts and terminology

Software safety issues become important when computers are used to control real-time, safety-critical processes. This survey attempts to explain why there is a problem, what the problem is, and what is known about how to solve it. Since this is a relatively new software research area, emphasis is placed on delineating the outstanding issues and research topics.

/pdf/software-safety-why-what-and-how-44olmi9ii7.pdf

Software safety: why, what, and how

Understanding usage patterns in wireless local-area networks (WLANs) is critical for those who develop, deploy, and manage WLAN technology, as well as those who develop systems and application software for wireless networks. This paper presents results from the largest and most comprehensive trace of network activity in a large, production wireless LAN. For eleven weeks we traced the activity of nearly two thousand users drawn from a general campus population, using a campus-wide network of 476 access points spread over 161 buildings. Our study expands on those done by Tang and Baker, with a significantly larger and broader population.We found that residential traffic dominated all other traffic, particularly in residences populated by newer students; students are increasingly choosing a wireless laptop as their primary computer. Although web protocols were the single largest component of traffic volume, network backup and file sharing contributed an unexpectedly large amount to the traffic. Although there was some roaming within a network session, we were surprised by the number of situations in which cards roamed excessively, unable to settle on one access point. Cross-subnet roams were an especial problem, because they broke IP connections, indicating the need for solutions that avoid or accommodate such roams.

/pdf/analysis-of-a-campus-wide-wireless-network-2hx2g1ldjf.pdf

Analysis of a campus-wide wireless network

In this paper, we propose cyber foraging: a mechanism to augment the computational and storage capabilities of mobile devices. Cyber foraging uses opportunistically discovered servers in the environment to improve the performance of interactive applications and distributed file systems on mobile clients. We show how the performance of distributed file systems can be improved by staging data at these servers even though the servers are not trusted. We also show how the performance of interactive applications can be improved via remote execution. Finally, we present VERSUDS: a virtual interface to heteregeneous service discovery protocols that can be used to discover these servers.

https://apollo.smu.edu.sg/papers/cyberforaging_sigops.pdf

The case for cyber foraging

The increasing cost of computer system failure has stimulated interest in improving software reliability. One way to do this is by adding redundant structural data to data structures. Such redundancy can be used to detect and correct (structural) errors in instances of a data structure. The intuitive approach of this paper, which makes heavy use of examples, is complemented by the more formal development of the companion paper, "Redundancy in Data Structures: Some Theoretical Results."

Redundancy in Data Structures: Improving Software Fault Tolerance

Explaining policies of Markov Decision Processes (MDPs) is complicated due to their probabilistic and sequential nature We present a technique to explain policies for factored MDP by populating a set of domain-independent templates We also present a mechanism to determine a minimal set of templates that, viewed together, completely justify the policy Our explanations can be generated automatically at run-time with no additional effort required from the MDP designer We demonstrate our technique using the problems of advising undergraduate students in their course selection and assisting people with dementia in completing the task of handwashing We also evaluate our explanations for course-advising through a user study involving students

/pdf/minimal-sufficient-explanations-for-factored-markov-decision-135v1c4iw9.pdf

Minimal sufficient explanations for factored Markov Decision Processes

Mobile applications execute in an environment characterized by scarce and dynamically varying resources. We believe that applications have to adapt dynamically and transparently to the amount of resources available at runtime. To achieve this goal, we use the conventional extension of the clientserver model to a client-proxy-server model. The mobile devices execute the client, which provides the user interface and some part of the application logic. The proxy is a component of the application that executes in the wired network to support the client. As the user moves, the proxy may also move to remain on the communication path from the mobile device to a fixed correspondent host. Logically, the proxy hides the “mobile” client from the server, who thinks it communicates with a standard client (i.e., a client that executes on a powerful desktop directly connected to the wired network). The new contribution of our research lies in the division of labor between client and proxy. The application logic of the “standard client” is split dynamically between the mobile client and the proxy, using mobile code, to adapt to the dynamic wireless environment and to address the limitations of the portable device. Using mobile code allows us to experiment with different adaptation strategies and to explore resource tradeoffs in a unified framework. We are developing the components of a flexible and general-purpose runtime infrastructure to facilitate the rapid development and deployment of such adaptive mobile applications. We will evaluate our infrastructure by implementing a number of wireless applications and by building simulation tools to validate the scalability of our architecture when considering metropolitan and provincial cellular systems. The simulations will be driven by trace data that we are collecting in cooperation with a Canadian cellular service provider.

/pdf/an-architecture-for-adaptive-mobile-applications-3db7kkkbrr.pdf

An architecture for adaptive mobile applications

Designing and implementing a visual debugger for distributed programs is a significant challenge. Distributed applications are often large and frequently exhibit a high degree of complexity. Consequently, a debugger must address problems of complexity and scale in at least two ways. First, appropriate user interfaces should allow a user to manage the vast amount of information typically obtained from distributed executions. Second, the tool itself, in handling this information, should be implemented efficiently, providing a user with reasonable response times for interactive use. Our research efforts, concentrating on these problems, have led to the development of Poet, a tool for the collection and presentation of event-based traces of distributed executions. Poet makes as few assumptions as possible about characteristics that must be possessed by all target environments. Information describing each target environment is placed in configuration files, allowing a single set of Poet executables to be used for all target environments. Comparing Poet's performance to XPVM, the standard visualization tool for PVM executions, reveals that this target-system independence does not impose a performance penalty.

POET: Target-system-independent visualizations of complex distributed-application executions

Distributed applications written in Hermes typically consist of a large number of sequential processes. The use of a hierarchy of process clusters can facilitate the debugging of such applications. Ideally, such a hierarchy should be derived automatically. This paper discusses two approaches to automatic process clustering, one analyzing runtime information with a statistical approach and one utilizing additional semantic information. Tools realizing these approaches were developed and a quantitative measure to evaluate process clusters is proposed. The results obtained under both approaches are compared, and indicate that the additional semantic information improves the cluster hierarchies derived. We demonstrate the value of automatic process clustering with an example. It is shown how appropriate process clusters reduce the complexity of the understanding process, facilitating program maintenance activities such as debugging. >

James P. Black

Papers

Redundancy in Data Structures: Improving Software Fault Tolerance

Minimal sufficient explanations for factored Markov Decision Processes

An architecture for adaptive mobile applications

POET: Target-system-independent visualizations of complex distributed-application executions

Using automatic process clustering for design recovery and distributed debugging