@misc{cryptoeprint:2004:065,
author = {Ian Blake, Kumar Murty, and Guangwu Xu},
title = {Refinements of Miller's Algorithm for Computing Weil/Tate Pairing},
howpublished = {Cryptology ePrint Archive, Report 2004/065},
year = {2004},
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.