@misc{cryptoeprint:2012:201,
author = {J.H.Zhang, Y.B.Cui},
title = {Comment an Anonymous Multi-receiver Identity-based Encryption Scheme},
howpublished = {Cryptology ePrint Archive, Report 2012/201},
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.