@misc{cryptoeprint:2014:998,
author = {Gus Gutoski and Douglas Stebila},
title = {Hierarchical deterministic Bitcoin wallets that tolerate key leakage},
howpublished = {Cryptology ePrint Archive, Report 2014/998},
year = {2014},
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.