Cryptology ePrint Archive: BibTeX Citation of Report 2009/126

@misc{cryptoeprint:2009:126,
    author = {Siamak F Shahandashti and Reihaneh Safavi-Naini},
    title = {Threshold Attribute-Based Signatures and Their Application to Anonymous Credential Systems},
    howpublished = {Cryptology ePrint Archive, Report 2009/126},
    year = {2009},
    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.