@misc{cryptoeprint:2007:216,
author = {Pawel Pszona and Grzegorz Stachowiak},
title = {Unlinkable Divisible Digital Cash without Trusted Third Party},
howpublished = {Cryptology ePrint Archive, Report 2007/216},
year = {2007},
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.