@misc{cryptoeprint:2012:628,
author = {Muhammad Yasir Malik},
title = {Efficient Group Key Management Schemes for Multicast Dynamic Communication Systems},
howpublished = {Cryptology ePrint Archive, Report 2012/628},
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.