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An Efficient File Hierarchy Walker
 In Proc. of the Summer '89 Usenix Conference
, 1989
"... This paper presents an interface specification and an efficient implementation of a general purpose library routine, ftwalk, to traverse a UNIX * file system hierarchy. A number of standard file system utilities, e.g., find, ls, rm, and others have been reimplemented using ftwalk. The total source c ..."
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This paper presents an interface specification and an efficient implementation of a general purpose library routine, ftwalk, to traverse a UNIX * file system hierarchy. A number of standard file system utilities, e.g., find, ls, rm, and others have been reimplemented using ftwalk. The total source code size is 30 % smaller and the efficiency of all commands improves. More importantly, these commands now handle the file system search in a uniform, robust, and secure manner. New tools have been built with ftwalk. A file system perusing tool, tw, will be described. tw subsumes the functionality of find and xargs. Further, it provides a powerful expression language with a syntax similar to C. For typical applications in which commands are executed on generated file names, tw is 5 to 10 times faster than find. The combination of a powerful language and performance efficiency in tw should reduce the practice of adding directory recursion to commands. 1.
KIST: A new encryption algorithm based on splay
"... In this paper, we proposed a new encryption algorithm called KIST. This algorithm uses an asynchronous key sequence and a splay tree. It is very efficient in the usage of both space and time. Some elementary security tests have been done. Key words asynchronous key sequence, splay tree, symmetric ke ..."
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In this paper, we proposed a new encryption algorithm called KIST. This algorithm uses an asynchronous key sequence and a splay tree. It is very efficient in the usage of both space and time. Some elementary security tests have been done. Key words asynchronous key sequence, splay tree, symmetric key encryption 1
Nearentropy hotlink assignments
 In Proceedings of the 14th Annual European Symposium on Algorithms (ESA
, 2006
"... Abstract. Consider a rooted tree T of arbitrary maximum degree d representing a collection of n web pages connected via a set of links, all reachable from a source home page represented by the root of T. Each web page i carries a weight wi representative of the frequency with which it is visited. By ..."
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Abstract. Consider a rooted tree T of arbitrary maximum degree d representing a collection of n web pages connected via a set of links, all reachable from a source home page represented by the root of T. Each web page i carries a weight wi representative of the frequency with which it is visited. By adding hotlinks — shortcuts from a node to one of its descendents — we wish to minimize the expected number of steps l needed to visit pages from the home page, expressed as a function of the entropy H(p) of the access probabilities p. This paper introduces several new strategies for effectively assigning hotlinks in a tree. For assigning exactly one hotlink per node, our method guarantees an upper bound on l of 1.141H(p)+1 if d> 2 and 1.08H(p)+2/3 if d = 2. We also present the first efficient general methods for assigning at most k hotlinks per node in trees of arbitrary maximum degree, achieving bounds on l of at most
Queaps
, 2002
"... We present a new priority queue data structure, the queap, that executes insertion in O(1) amortized time and extractmin in O(log(k + 2)) amortized time if there are k items that have been in the heap longer than the item to be extracted. Thus if the operations on the queap are rstin rstout ..."
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We present a new priority queue data structure, the queap, that executes insertion in O(1) amortized time and extractmin in O(log(k + 2)) amortized time if there are k items that have been in the heap longer than the item to be extracted. Thus if the operations on the queap are rstin rstout, as on a queue, each operation will execute in constant time. This idea of trying to make operations on the least recently accessed items fast, which we call the queueish property, is a natural complement to the working set property of certain data structures, such as splay trees and pairing heaps, where operations on the most recently accessed data execute quickly. However, we show that the queueish property is in some sense more dicult than the working set property by demonstrating that it is impossible to create a queueish binary search tree, but that many search data structures can be made almost queueish with a O(log log n) amortized extra cost per operation.
Open Data Structures (in Java)
"... I am grateful to Nima Hoda, who spent a summer tirelessly proofreading many of the chapters in this book, and to the students in the Fall 2011 offering of COMP2402/2002, who put up with the first draft of this book and spotted many typographic, grammatical, and factual errors in the first draft. i W ..."
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I am grateful to Nima Hoda, who spent a summer tirelessly proofreading many of the chapters in this book, and to the students in the Fall 2011 offering of COMP2402/2002, who put up with the first draft of this book and spotted many typographic, grammatical, and factual errors in the first draft. i Why This Book? There are plenty of books that teach introductory data structures. Some of them are very good. Most of them cost money, and the vast majority of computer science undergraduate students will shellout at least some cash on a data structures book. Thereareafewfreedatastructuresbooksavailableonline. Someareverygood,but most of them are getting old. The majority of these books became free when the author and/or publisher decided to stop updating them. Updating these books is usually not
Improvement on Intrusion Detection Technology Based on Protocol Analysis and Pattern Matching
"... With the development of highspeed network technique and increasing volume of network traffic, traditional pattern matching method can’t adapt to the new challenges to intrusion detection. To solve this, protocol analysis is introduced into the procedure of intrusion detection, and it has advantages ..."
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With the development of highspeed network technique and increasing volume of network traffic, traditional pattern matching method can’t adapt to the new challenges to intrusion detection. To solve this, protocol analysis is introduced into the procedure of intrusion detection, and it has advantages such as the capability of detailed command parsing, attack detection and protocol acknowledgement against fragment attacks, the lower false positives and high performance. By the integration with pattern matching, intrusion detection technology based on protocol analysis may significantly reduce the amount of computation and improve the efficiency of packet analysis as well as the detection rates.
Open Data Structures (in C++)
"... I am grateful to Nima Hoda, who spent a summer tirelessly proofreading many of the chapters in this book, and to the students in the Fall 2011 offering of COMP2402/2002, who put up with the first draft of this book and spotted many typographic, grammatical, and factual errors in the first draft. i P ..."
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I am grateful to Nima Hoda, who spent a summer tirelessly proofreading many of the chapters in this book, and to the students in the Fall 2011 offering of COMP2402/2002, who put up with the first draft of this book and spotted many typographic, grammatical, and factual errors in the first draft. i Preface to the C++ Edition This book is intended to teach the design and analysis of basic data structures and their implementation in an objectoriented language. In this edition, the language happens to be C++. This book is not intended to act as an introduction to the C++ programming language. Readers of this book need only be familiar with the basic syntax of C++ and similar languages. Those wishing to work with the accompanying source code should have some experience programming in C++. This book is also not intended as an introduction to the C++ Standard Template Library or the generic programming paradigm that the STL embodies. This book describes implementations of several different data structures, many of which are used in implementations
Cryptanalysis of splay tree based encryption
"... Abstract. We present a chosenplaintext attack on KIST, a recently proposed encryption scheme based on splay trees. Our attack recovers a 128bit key with approximately 2 28 bit operations and fewer than 2 19 chosenplaintext queries. Splay trees are a type of binary search search trees discovered b ..."
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Abstract. We present a chosenplaintext attack on KIST, a recently proposed encryption scheme based on splay trees. Our attack recovers a 128bit key with approximately 2 28 bit operations and fewer than 2 19 chosenplaintext queries. Splay trees are a type of binary search search trees discovered by Sleator and Tarjan in 1983 [1, 2]. Splay trees are selfadjusting, in the sense that a tree modifies itself at each access to a node—the modification being called “splaying”. In 1988, Jones proposed [3] a simplification of splay trees to compress data, and proposed to use splay trees to encrypt data using a similar method with as key a secret initial tree. The (rather old) word processor Lotus Ami Pro included a basic, deliberately insecure, version of splay tree based encryption to allow export [4]. As the basic version of splay tree based encryption is insecure, Jones proposed [5] two techniques to strengthen that scheme. Recently, Wei and Zeng argued [6] that Jones ’ strengthened schemes are also insecure, and proposed a new encryption scheme based on splay trees, called KIST. Below we describe a chosenplaintext attack for that new scheme. We refer to [6] for a description of KIST. Our attack is based on the following observations: