@misc{cryptoeprint:2015:195,
author = {Stephanie Bayer and Jens Groth},
title = {Zero-knowledge Argument for Polynomial Evaluation with Application to Blacklists},
howpublished = {Cryptology ePrint Archive, Report 2015/195},
year = {2015},
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.