@misc{cryptoeprint:2008:353,
author = {Prasanth Kumar Thandra and S.A.V. Satya Murty and R Balasubramanian},
title = {Weaknesses in HENKOS Stream Cipher},
howpublished = {Cryptology ePrint Archive, Report 2008/353},
year = {2008},
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.