Masters Degrees (Computer Science)

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Static analysis of regular expressions
(Stellenbosch : Stellenbosch University, 2017-11-19) Weideman, Nicolaas Hendrik; Van der Merwe, Andries Brink; Stellenbosch University. Faculty of Science. Dept. of Mathematical Sciences. Division Computer Science.
ENGLISH ABSTRACT : Regular expressions are widely used throughout the programming community. In most cases, regular expressions allow for pattern matching tasks to be performed efficiently, but in some instances regular expression matching can be extremely slow. The exploit of the potential slowness of regular expression matching, is known as a regular expression denial of service attack. We investigate regular expression denial of service attacks, by approaching it from a computational complexity and automata theoretic point of view. A method for accurately modeling the matching time behaviour of a backtracking regular expression matcher, by using automata theoretic methods, is presented. We analyze our models by using the concept of ambiguity in nondeterministic finite-state automata. Our approach is evaluated on repositories of regular expressions often used in practice. Techniques for mitigating the vulnerability of backtracking regular expression matchers are investigated as a means to thwart regular expression denial of service attacks.