103 research outputs found
The RSA Algorithm and PGP
No full textThis write-up gives a complete in-depth derivation of the RSA algorithm, based on a proof for Euler's Theorem. The implementation of the algorithm in the PGP software written by Phil Zimmermann will be discussed, as well as the two other important algorithms used in PGP, IDEA and MD5. The last section provides a crash course in using PGP. 1 Introduction Public-key cryptography has recently become the focus of public attention as governments in and outside the U.S. try to regulate information flow on the Internet. What is public-key cryptography about? The following concise explanation from Phil Zimmermann can be found in [1] Pretty Good(tm) Privacy (PGP), from Phil's Pretty Good Software, is a high security cryptographic software application for MSDOS, Unix, VAX/VMS, and other computers. PGP allows people to exchange files or messages with privacy, authentication, and convenience. Privacy means that only those intended to receive a message can read it. Authentication means that messag..
Drawing the Red Line in Java
No full textSoftware-based protection has become a viable alternative to hardware-based protection in systems based on languages such as Java, but the absence of hardware mechanisms for protection has been coupled with an absence of a user/kernel boundary. We show why such a "red line" must be present in order for a Java virtual machine to be as effective and as reliable as an operating system. We discuss how the red line can be implemented using software mechanisms, and explain the ones we use in the Java system that we are building. 1. Introduction A paper that appeared at a previous HotOS [4] stated that "protection is a software issue." This statement is incomplete; we would reword it as "Protection is a software issue, but it is not the only software issue." In particular, issues such as resource control, communication, and termination need to be dealt with in software if hardware protection mechanisms are not present. To date, systems that replace hardware mechanisms with software mechanism..
Web Services and Widgets for Library Information Systems
Get PDFAs more libraries integrate information from web services to enhance their online public displays, techniques that facilitate this integration are needed. This paper presents a technique for such integration that is based on HTML widgets. We discuss three example systems (Google Book Classes, Tictoclookup, and MAJAX) that implement this technique. These systems can be easily adapted without requiring programming experience or expensive hosting
Perfctr-Xen
No full textVirtualization is a powerful technique used for variety of application domains, including emerging cloud environments that provide access to virtual machines as a service. Because of the interaction of virtual machines with multiple underlying software and hardware layers, the analysis of the performance of applications running in virtualized environments has been difficult. Moreover, performance analysis tools commonly used in native environments were not available in virtualized environments, a gap which our work closes.
This paper discusses the challenges of performance monitoring inherent to virtualized environments and introduces a technique to virtualize access to low-level performance counters on a per-thread basis. The technique was implemented in perfctr-xen, a framework for the Xen hypervisor that provides an infrastructure for higher-level profilers. This framework supports both accumulative event counts and interrupt-driven event sampling. It is light-weight, providing direct user mode access to logical counter values. perfctr-xen supports multiple modes of virtualization, including paravirtualization and hardware-assisted virtualization. perfctr-xen applies guest kernel-hypervisor coordination techniques to reduce virtualization overhead. We present experimental results based on microbenchmarks and SPEC CPU2006 macrobenchmarks that show the accuracy and usability of the obtained measurements when compared to native execution.</jats:p
MJ - A System for Constructing Bug-Finding Analyses for Java
No full textMany software defects result from the violation of programming rules: rules that describe how to use a programming language and its libraries and rules that describe the dos and don'ts within a given application, library or system. MJ is a language and an engine that can succinctly express many of these rules for programs written in Java. MJ programs are checkers that are compiled into compiler extensions. A static analysis engine applies the extensions to user code and flags rule violations. We have implemented and tested several extensions in MJ for both general and application-specific rules. Our checkers have found dozens of bugs in some widely-deployed and mature software systems. 1
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