ABSTRACT
This chapter presents how to use Attribute-Based Encryption schemes to build a collusion resistant Optimal Group Key management scheme, and addresses both the collusion issue and ciphertext size issue. Basically, the ciphter-text size is proportional to the number of used attributes in the encryption based on existing Ciphertext-Policy Attribute-Based Encryption solutions. The communication model of Optimal Group Key is based on multicast. Thus, only legitimated group members should have access to update-to-date Group Keys when group members join or leave the group dynamically. This requirement is usually achieved through a group rekeying procedure, in which a centralized group controller updates key material for all legitimate group members. Group membership removal is usually more challenging than group membership addition because the number of impacted group members is exponentially large.
