Probabilistic Latent Semantic Analysis (PLSA) is an effective technique for information retrieval, but it has a serious drawback: it consumes a huge amount of computational resources, so it is hard to train this model on a large collection of documents. The aim of this paper is to improve time efficiency of the training algorithm. Two different approaches are explored: one is based on efficient...

Joux’s multicollision attack is one of the most striking results on hash functions and also one of the simplest: it computes a k-collision on iterated hashes in time ⌈log2 k⌉ · 2 , whereas k! · 2 was thought to be optimal. Kelsey and Schneier improved this to 3 · 2 if storage 2 is available and if the compression functions admits easily found fixed-points. This paper presents a simple technique...

Center for Information Technology Integration University of Michigan 519 West William Street Ann Arbor, MI 48103-4943 CITI Technical Report 92-3