@misc{cryptoeprint:2013:249,
author = {Kaoru Kurosawa and Takuma Ueda},
title = {How to Factor N_1 and N_2 When p_1=p_2 mod 2^t},
howpublished = {Cryptology ePrint Archive, Report 2013/249},
year = {2013},
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.