@misc{cryptoeprint:2011:495,
author = {Dario Catalano and Dario Fiore},
title = {Vector Commitments and their Applications},
howpublished = {Cryptology ePrint Archive, Report 2011/495},
year = {2011},
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.