@misc{cryptoeprint:2010:023,
author = {Junko Takahashi and Toshinori Fukunaga},
title = {Differential Fault Analysis on AES with 192 and 256-Bit Keys},
howpublished = {Cryptology ePrint Archive, Report 2010/023},
year = {2010},
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.