Contents muticast method enabling determination of leakage origin and exclusion

For delivering expensive contents like digital cinema, it is important to discover malicious sites and stop content leakage. We propose a multicast contents delivery method that allows malicious sites to be identified and immediately halts delivery, while continuing to deliver the contents to valid destinations. We apply multicast watermarking to discover malicious sites and broadcast encryption to exclude said sites. We evaluate the processing time of broadcast encryption in software on a PC. It is shown that this method can multicast contents to up to 2000 destinations with sufficiently small processing time. The results show that secure digital cinema multicast delivery can be realized.