@misc{cryptoeprint:2004:149,
author = {E. Trichina and L. Korkishko},
title = {Secure and Efficient AES Software Implementation for Smart Caards},
howpublished = {Cryptology ePrint Archive, Report 2004/149},
year = {2004},
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.