Access key distribution scheme for level-based hierarchy

A new access key distribution scheme is proposed for applications where users are in a level-based hierarchy. Based on Chinese remainder theorem (CRT) and Rabin-based secure public key cryptosystem, the proposed scheme has the following characteristics: (1) each user can derive the secret key for user in a lower security level and the inversion is not allowed; (2) the key generation and derivation algorithms are simple; (3) the user and secret key selection are flexible; (4) semantic security can be ensured to prevent attacking from users with lower privileges.