Department of Computer Science | Institute of Theoretical Computer Science | CADMO

Theory of Combinatorial Algorithms

Prof. Emo Welzl and Prof. Bernd Gärtner

Mittagsseminar (in cooperation with M. Ghaffari, A. Steger and B. Sudakov)

Mittagsseminar Talk Information

Date and Time: Tuesday, May 04, 2010, 12:15 pm

Duration: This information is not available in the database

Location: CAB G51

Speaker: Mohammad Torabi Dashti (D-INFK - Information Security)

Constructing and recognizing permutation-complete words

Permutation-complete words contain all the permutations of 1 .. N, for some positive natural N. Here w contains w' iff w' can be found by erasing zero or more letters from w. In 1972, Karp [1] posed the problem of finding the length of a shortest permutation-complete word, given a positive natural N. The problem is still open.

Recently, Mauw, Radomirovic and Torabi Dashti [2] proved that the message complexity of N-party contract signing protocols is tightly related to the length of shortest permutation-complete words. This result in particular implies that efficient algorithms for constructing (resp. recognizing) permutation-complete words can be used for designing (resp. debugging) N-party contract signing protocols. The talk will give an overview on the combinatorial aspects of constructing and recognizing permutation-complete words.

[1] Vaclav Chvátal, David Klarner, Donald Knuth: Selected Combinatorial Research Problems. Technical Report: CS-TR-72-292. Stanford University, 1972.
[2] Sjouke Mauw, Sasa Radomirovic, Mohammad Torabi Dashti: Minimal Message Complexity of Asynchronous Multi-party Contract Signing. CSF 2009, IEEE Computer Society.

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