Content and Key Management to Trace Traitors in Broadcasting Services

Traitor tracing encryption schemes are a type of broadcasting encryption and have been developed for broadcasting services. There are multiple distinct decryption keys for each encryption key, and each service subscriber is given a unique decryption key. Any subscriber that redistributes his or her decryption key to a third party or who uses it to make a pirate receiver $$\mathcal{PR}$$ can be identified using the schemes. However, almost all previous schemes are effective against only those $$\mathcal{PR}$$s with only one decryption key. We first discuss an attack content comparison attack against the above encryption schemes. The attack involves multiple distinct decryption keys and content-data comparison mechanism. We have developed a content and key management methodCKM that makes traitor tracing schemes secure against the content comparison attack. Its use makes it impossible for $$\mathcal{PR}$$s to distinguish ordinary content data from test data and makes traitor tracing schemes effective against all $$\mathcal{PR}$$s. The CKM makes the broadcasting services secure.