@misc{cryptoeprint:2007:274,
    author = {Chunbo Ma, Jun Ao, and Jianhua Li},
    title = {Group-based Proxy Re-encryption scheme},
    howpublished = {Cryptology ePrint Archive, Report 2007/274},
    year = {2007},
    url = {http://eprint.iacr.org/2007/274},
}