International Association for Cryptologic Research
The authors introduce Policy-Based Signatures (PBS), where a signer can only sign messages conforming to some authority-specified policy. The main requirements are unforgeability and privacy, the latter meaning that signatures not reveal the policy. PBS offers value along two fronts: on the practical side, they allow a corporation to control what messages its employees can sign under the corporate key. On the theoretical side, they unify existing paper, capturing others forms of signatures as special cases or allowing them to be easily built.