@misc{cryptoeprint:2013:323,
author = {Tsz Hon Yuen and Ye Zhang and Siu-Ming Yiu},
title = {Encryption Schemes with Post-Challenge Auxiliary Inputs},
howpublished = {Cryptology ePrint Archive, Report 2013/323},
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.