@misc{cryptoeprint:2009:595,
    author = {Endre Bangerter and Jan Camenisch and Stephan Krenn},
    title = {Efficiency Limitations for $\Sigma$-Protocols for Group Homomorphisms},
    howpublished = {Cryptology ePrint Archive, Report 2009/595},
    year = {2009},
    url = {http://eprint.iacr.org/2009/595},
}