@misc{cryptoeprint:2011:211,
author = {Nicolas T. Courtois},
title = {Security Evaluation of GOST 28147-89 In View Of International Standardisation},
howpublished = {Cryptology ePrint Archive, Report 2011/211},
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.