@misc{cryptoeprint:2007:114,
author = {Guang Zeng and Wenbao Han and Kaicheng He},
title = {High Efficiency Feedback Shift Register: $\sigma-$LFSR},
howpublished = {Cryptology ePrint Archive, Report 2007/114},
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.