@misc{cryptoeprint:2007:149,
author = {Ki Hyoung Ko and Jang Won Lee and Tony Thomas},
title = {Towards Generating Secure Keys for Braid Cryptography},
howpublished = {Cryptology ePrint Archive, Report 2007/149},
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.