@misc{cryptoeprint:2009:181,
author = {Erik-Oliver Blass and Anil Kurmus and Refik Molva and Thorsten Strufe},
title = {PSP: Private and Secure Payment with RFID},
howpublished = {Cryptology ePrint Archive, Report 2009/181},
year = {2009},
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.