@misc{cryptoeprint:2012:054,
author = {Emiliano De Cristofaro and Gene Tsudik},
title = {On the performance of certain Private Set Intersection protocols},
howpublished = {Cryptology ePrint Archive, Report 2012/054},
year = {2012},
note = {\url{http://eprint.iacr.org/}},
}
You will need the url.sty package (comes with most LaTeX installations) for the last line. Otherwise, remove the \url command.