@misc{cryptoeprint:2012:065,
author = {Tsukasa Ishiguro},
title = {Modified version of “Latin Dances Revisited: New Analytic Results of Salsa20 and ChaCha”},
howpublished = {Cryptology ePrint Archive, Report 2012/065},
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.