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Section: Software

Keywords : Tree automata, approximations, term rewriting systems.

Timbuk: a tree automata library

Participant : Thomas Genet.

Timbuk  [41] is a library of Ocaml functions for manipulating tree automata. More precisely Timbuk deals with finite bottom-up tree automata (deterministic or not). This library provides the classical operations over tree automata, viz , the boolean operations (intersection, union, complement), emptiness and inclusion checking, renaming, determinisation, transition normalisation, and a mechanism for building the tree automaton recognizing the set of irreducible terms for a left-linear TRS. This library also implements some more specific algorithms that we use for verification (of cryptographic protocols in particular):

This software is distributed under the Gnu Library General Public License and is freely available at http://www.irisa.fr/lande/genet/timbuk/ . Timbuk has been registered at the APP with number IDDN.FR.001.20005.00.S.P.2001.000.10600.

Timbuk in version 2.1. This version contains several optimisations and utilities. The completion algorithm complexity has been optimised for better performance in space and time. Timbuk now provides two ways to achieve completion: a dynamic version which permits to compute approximation step by step and a static version which pre-compiles matching and approximation in order to enhance speed of completion. Timbuk 2.1 also provides a graphical interface called Tabi for browsing tree automata and figure out more easily what are the recognized language, as well as Taml an Ocaml toplevel with basic functions on tree automata. Timbuk 2.1 has been used for a case study done with Thomson-Multimedia for cryptographic protocol verification.

Timbuk is used by other research groups to achieve cryptographic protocol verification. Frédéric Oehl and David Sinclair of Dublin University use it in an approach combining a proof assistant (Isabelle/HOL) and approximations (done with Timbuk)  [52] , [51] . Pierre-Cyrille Heam, Yohan Boichut and Olga Kouchnarenko of the Cassis Inria project use Timbuk as a verification back-end  [45] for AVISPA  [32] . AVISPA is a powerful tool for verifying cryptographic protocols defined in high level protocol specification format. More recently, Timbuk was also used at LIAFA by Gael Patin, Mihaela Sighireanu and Tayssir Touili to design the SPADE tool whose purpose is to model-check multi-threaded and recursive programs.


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