@misc{cryptoeprint:2013:721,
author = {Bo Yang and Zhao Yang and Zibi Xiao and Shougui Li},
title = {Deep Attacks of a Certificateless Signature Scheme},
howpublished = {Cryptology ePrint Archive, Report 2013/721},
year = {2013},
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.