@misc{cryptoeprint:2013:023,
author = {Jong Hwan Park and Dong Hoon Lee},
title = {A New Practical Identity-Based Encryption System},
howpublished = {Cryptology ePrint Archive, Report 2013/023},
year = {2013},
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.