Blocking Java Applets at the Firewall

This paper explores the problem of protecting a site on the Internet against hostile external Java applets while allowing trusted internal applets to run. With careful implementation, a site can be made resistant to current Java security weaknesses as well as those yet to be discovered. In addition, we describe a new attack on certain sophisticated firewalls that is most effectively realized as a Java applet

Splay Trees for Data Compression

We present applications of splay trees to two topics in data compression. First is a variant of the move-to-front (mtf) data compression (of Bentley,Sleator Tarjan and Wei) algorithm, where we introduce secondary list(s). This seems to capture higher-order correlations. An implementation of this algorithm with Sleator-Tarjan splay trees runs in time (provably) proportional to the entropy of the input sequence. When tested on some telephony data, compression ratio and run time showed significant improvements over original mtf-algorithm, making it competitive or better than popular programs. For stationary ergodic sources, we analyse the compression and output distribution of the original mtf-algorithm, which suggests why the secondary list is appropriate to introduce. We also derive analytical upper bounds on the average codeword length in terms of stochastic parameters of the source. Secondly, we consider the compression (or coding) of source sequences where the codewords are required ..

Rio: Storing Files Reliably in Memory

Abstract: Memory is currently a second-class citizen of the storage hierarchy because of its vulnerability to power failures and software crashes. Designers have traditionally sacrificed either reliability or performance when using memory as a cache for disks; our goal is to do away with this tradeoff by making memory as reliable as disks. The Rio (RAM I/O) project at Michigan is modifying the Digital Unix (formerly OSF/1) kernel to protect the file cache from operating system crashes. If successful, making memory as reliable as disks will 1) improve file cache performance to that of a pure write-back scheme by eliminating all reliability-caused writes to disk; 2) improve reliability to that of a write-through scheme by making memory a reliable place to store files long term; and 3) simplify applications such as file systems and databases by eliminating write-back daemons and complex commit and checkpointing protocols.

Rio: Storing Files Reliably in Memory

: Memory is currently a second-class citizen of the storage hierarchy because of its vulnerability to power failures and software crashes. Designers have traditionally sacrificed either reliability or performance when using memory as a cache for disks; our goal is to do away with this tradeoff by making memory as reliable as disks. The Rio (RAM I/O) project at Michigan is modifying the Digital Unix (formerly OSF/1) kernel to protect the file cache from operating system crashes. If successful, making memory as reliable as disks will 1) improve file cache performance to that of a pure write-back scheme by eliminating all reliability-caused writes to disk; 2) improve reliability to that of a write-through scheme by making memory a reliable place to store files long term; and 3) simplify applications such as file systems and databases by eliminating write-back daemons and complex commit and checkpointing protocols. 1 Introduction As processors continue to double in speed every year or tw..