@misc{cryptoeprint:2006:203,
author = {Sanjit Chatterjee and Palash Sarkar},
title = {Generalization of the Selective-ID Security Model for HIBE Protocols},
howpublished = {Cryptology ePrint Archive, Report 2006/203},
year = {2006},
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.