@misc{cryptoeprint:2012:650,
author = {Ben Smyth and Mark D. Ryan and Liqun Chen},
title = {Formal analysis of privacy in Direct Anonymous Attestation schemes},
howpublished = {Cryptology ePrint Archive, Report 2012/650},
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.