@misc{cryptoeprint:2006:376,
author = {Vlastimil KLIMA},
title = {A New Concept of Hash Functions SNMAC Using a Special Block Cipher and NMAC/HMAC Constructions},
howpublished = {Cryptology ePrint Archive, Report 2006/376},
year = {2006},
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.