Cryptology ePrint Archive: BibTeX Citation of Report 2015/684

@misc{cryptoeprint:2015:684,
    author = {Aggelos Kiayias and Yona Raekow and Alexander Russell and Narasimha Shashidhar},
    title = {A One-time Stegosystem and Applications to Efficient Covert Communication},
    howpublished = {Cryptology ePrint Archive, Report 2015/684},
    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.