Cryptology ePrint Archive: BibTeX Citation of Report 2008/131

@misc{cryptoeprint:2008:131,
    author = {Sebastiaan Indesteege and Florian Mendel and Bart Preneel and Christian Rechberger},
    title = {Collisions and other Non-Random Properties for Step-Reduced SHA-256},
    howpublished = {Cryptology ePrint Archive, Report 2008/131},
    year = {2008},
    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.