Key points are not available for this paper at this time.
A scheme based on cryptography is proposed for access control in a system where hierarchy is represented by a partially ordered set (or poset). Straightforward implementation of the scheme requires users highly placed in the hierarchy to store a large number of cryptographic keys. A timeversus-storage trade-off is then described for addressing this key management problem.
Akl et al. (Mon,) studied this question.