Abstract
With the continuous growth in network technology, the exchange of digital images, digital audio, and digital text data has become very common. Digital content can be easily duplicated and redistributed, and hence, the protection of copyrights and privacy is an important issue. For the protection of digital content, access control has been studied extensively. In this review, we summarize access control for digital content and key derivation. The introduction of hash chains reduces the number of managed keys to one. These schemes are also resilient to collusion attacks in which malicious users illegally access the multimedia content at a quality that is better than the quality allowed by their access rights.
