@misc{cryptoeprint:2011:632,
author = {Elena Dubrova},
title = {A Scalable Method for Constructing Galois NLFSRs with Period $2^n-1$ using Cross-Join Pairs},
howpublished = {Cryptology ePrint Archive, Report 2011/632},
year = {2011},
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.