@misc{cryptoeprint:2013:735,
author = {Michael Tunstall and Carolyn Whitnall and Elisabeth Oswald},
title = {Masking Tables---An Underestimated Security Risk},
howpublished = {Cryptology ePrint Archive, Report 2013/735},
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.