@misc{cryptoeprint:2003:165,
author = {Andreas Winter, Anderson C. A. Nascimento, Hideki Imai},
title = {Commitment Capacity of Discrete Memoryless Channels},
howpublished = {Cryptology ePrint Archive, Report 2003/165},
year = {2003},
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.