Abstract
Access control in a hierarchy refers to a selective access to a database. A large number of users work with the same database. These users are organized in a hierarchical structure and therefore have different access rights to the data. This paper offers a solution to the problem of access control in a hierarchy based on quantum cryptography. Each user has two keys: a classical key and a quantum key. Our scheme offers several security advantages over the classical schemes to date. It protects users from identity theft and prevents collusion attacks. Most importantly though, our scheme adapts to dynamic changes of the user hierarchy: users may join, leave, or change position in the hierarchy, without affecting the rest of the user structure.