@misc{cryptoeprint:2009:607,
    author = {Ghassan O. Karame and Srdjan Capkun},
    title = {Efficient Client Puzzles based on Repeated-Squaring},
    howpublished = {Cryptology ePrint Archive, Report 2009/607},
    year = {2009},
    url = {http://eprint.iacr.org/2009/607},
}