@misc{cryptoeprint:2008:544,
author = {Yalin Chen, Chun-Hui Huang, Jue-Sam Chou},
title = {Comments on two multi-server authentication protocols},
howpublished = {Cryptology ePrint Archive, Report 2008/544},
year = {2008},
note = {\url{https://ia.cr/2008/544}},
}
You will need the url.sty package (comes with most LaTeX installations) for the last line. Otherwise, remove the \url command.