@misc{cryptoeprint:2008:369,
author = {Shahram Khazaei and Willi Meier},
title = {New Directions in Cryptanalysis of Self-Synchronizing Stream Ciphers},
howpublished = {Cryptology ePrint Archive, Report 2008/369},
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.