Speaker: Theo Garefalakis, University of London Time: Wednesday, January 30, 1:30 p.m. Place: HP4369 School of Math and Stats, Carleton University Title: Lattice basis reduction in cryptanalysis: two recent results. abstract: Lattice basis reduction algorithms (such as the well known LLL algorithm) have had great success in cryptanalysis. We show how to use the LLL algorithm to attack the Digital Signature Algorithm if the nonces are chosen too small. Next we look at a factoring-based cryptosystem and show how it can be broken completely by reducing the problem to a Simultaneous Diophantine Approximation problem, which can be solved using LLL.