An RSA-Based Time-Bound Hierarchical Key Assignment Scheme for Electronic Article Subscription

1. An RSA-Based Time-Bound Hierarchical Key Assignment Scheme for Electronic Article Subscription

2. Electronic Article Subscription • ACM publishes lots of journals periodically • Different packages of journals for subscription options • Users subscribe packages for different time periods • Only subscribed users can access the journals published in the time periods the users subscribed to

3. Electronic Article Subscription • The journals can be just posted online, but encrypted • Each journal is encrypted by a different key • Each user has one user key • The user key can be used to decrypt only the journals the user are entitled to access

4. Key Assignment • All packages can be structured as a hierarchy • If a user subscribes a package p_i for time periods from t_1 to t_2, then a user key K_i,(t_1,t_2) will be assigned to the user • Each journal belong to package p_j, published in time t, will be encrypted by a key K_j,t

5. Key Derivation • K_i,(t_1,t_2) can derive K_j,t if and only if P_i is a higher package than P_j and t_1 ≤ t ≤ t_2

6. An Example