@misc{cryptoeprint:1997:006,
author = {Yuval Ishai and Eyal Kushilevitz},
title = {Protecting Data Privacy in Private Information Retrieval Schemes},
howpublished = {Cryptology ePrint Archive, Report 1997/006},
year = {1997},
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.