Paper 2007/363

Fuzzy Private Matching (Extended Abstract)

Łukasz Chmielewski and Jaap-Henk Hoepman

Abstract

In the private matching problem, a client and a server each hold a set of $n$ input elements. The client wants to privately compute the intersection of these two sets: he learns which elements he has in common with the server (and nothing more), while the server gains no information at all. In certain applications it would be useful to have a private matching protocol that reports a match even if two elements are only similar instead of equal. Such a private matching protocol is called \emph{fuzzy}, and is useful, for instance, when elements may be inaccurate or corrupted by errors. We consider the fuzzy private matching problem, in a semi-honest environment. Elements are similar if they match on $$ out of $$ attributes. First we show that the original solution proposed by Freedman et al. is incorrect. Subsequently we present two fuzzy private matching protocols. The first, simple, protocol has bit message complexity $$. The second, improved, protocol has a much better bit message complexity of $$, but here the client incurs a $$ factor time complexity. Additionally, we present protocols based on the computation of the Hamming distance and on oblivious transfer, that have different, sometimes more efficient, performance characteristics.