Multimedia security in the distributed environment

Multicast is very useful way for large-scale distributing multimedia over the network. It can significantly reduce the bandwidth required to transmit same multimedia over the network to multiple receivers. This property makes multicast competitive and attractive. We propose a simple and efficient scheme in order to resolve the issue mentioned above. In our scheme, the content provider generates two different watermarked packets for even´ data packet firstly. Next, he encrypts every two watermarked packets by two different keys, respectively. Finally, he multicasts all of encrypted packets with encrypted keys to intended receivers. In the receiver, only one of every pair of encrypted packets is decrypted relying on the ID stored in tamper-resistant hardware. Every receiver obtains unique watermarked packets because every ID is unique. So, the watermarked packets can be used to trace those receivers who make redistribution of received multimedia content illegally.