@inproceedings{backes06secure,
  author       = {Backes, Michael and Cachin, Christian and Oprea, Alina},
  title        = {Secure Key-Updating for Lazy Revocation},
  booktitle    = {Proceedings of 11th European Symposium on Research in Computer Security(ESORICS)},
  series       = {Lecture Notes in Computer Science},
  volume       = {4189},
  month        = {September},
  year         = {2006},
  publisher    = {Springer},
  pages        = {327-346},
  note         = {Preprint on IACR ePrint 2005/334}
}