@misc{cryptoeprint:2010:595,
author = {Hemanta K. Maji and Manoj Prabhakaran and Mike Rosulek},
title = {Attribute-Based Signatures},
howpublished = {Cryptology ePrint Archive, Report 2010/595},
year = {2010},
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.