Cryptology ePrint Archive: BibTeX Citation of Report 2015/639

@misc{cryptoeprint:2015:639,
    author = {Hao Chen},
    title = {Polynomial time reduction from approximate shortest vector problem to the principle ideal porblem for lattices in cyclotomic rings},
    howpublished = {Cryptology ePrint Archive, Report 2015/639},
    year = {2015},
    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.