@misc{cryptoeprint:2012:640,
author = {Gaoli Wang and Yanzhao Shen},
title = {Preimage and Pseudo-Collision Attacks on Step-Reduced SM3 Hash Function},
howpublished = {Cryptology ePrint Archive, Report 2012/640},
year = {2012},
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.