@misc{cryptoeprint:2012:351,
author = {Jean-Philippe Aumasson and Daniel J. Bernstein},
title = {SipHash: a fast short-input PRF},
howpublished = {Cryptology ePrint Archive, Report 2012/351},
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.