@misc{cryptoeprint:2000:028,
author = {Christian Cachin},
title = {An Information-Theoretic Model for Steganography},
howpublished = {Cryptology ePrint Archive, Report 2000/028},
year = {2000},
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.