@misc{cryptoeprint:2015:205,
author = {Jooyoung Lee},
title = {Towards Key-Length Extension with Optimal Security: Cascade Encryption and Xor-cascade Encryption},
howpublished = {Cryptology ePrint Archive, Report 2015/205},
year = {2015},
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.