@misc{cryptoeprint:2012:447,
author = {Zhaohui Tang and Hoon Wei Lim},
title = {Multi-receiver Homomorphic Authentication Codes for Network Coding},
howpublished = {Cryptology ePrint Archive, Report 2012/447},
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.