@misc{cryptoeprint:2003:073,
author = {Sunder Lal and Amit K Awasthi},
title = {A Scheme for obtaining a Warrant Message from the Digital Proxy Signatures},
howpublished = {Cryptology ePrint Archive, Report 2003/073},
year = {2003},
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.