@misc{cryptoeprint:2007:480,
author = {Junko Takahashi and Toshinori Fukunaga},
title = {Differential Fault Analysis on the AES Key Schedule},
howpublished = {Cryptology ePrint Archive, Report 2007/480},
year = {2007},
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.