@misc{cryptoeprint:2013:544,
author = {Christian Hanser and Daniel Slamanig},
title = {Warrant-Hiding Delegation-by-Certificate Proxy Signature Schemes},
howpublished = {Cryptology ePrint Archive, Report 2013/544},
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.