@misc{cryptoeprint:2013:318,
author = {Yutaka Kawai and Katsuyuki Takashima},
title = {Fully-Anonymous Functional Proxy-Re-Encryption},
howpublished = {Cryptology ePrint Archive, Report 2013/318},
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.