Key Management for Versatile Pay-TV Services

摘要

The content of pay-TV services is encrypted and each subscriber has a security module that holds a decryption key. When subscribers want to receive the same pay-TV services that they receive at home outside their homes, they have to bring the security module with them. However, it is not easy to take the module out of the TV set. To enrich current and conventional pay-TV services and to make it easier for subscribers to obtain pay-TV services outside their homes, we propose a key management system using a temporary key, an attribute-based encryption (ABE) scheme, and a mobile terminal. The temporary key is not a conventional key, but has a backward compatibility. The ABE is used to restrict the time and location when and where the temporary key can be used. The mobile terminal has a role to take secret data related to the temporary key and ABE. In this system, a certain decryption key sk_t is stored in the mobile terminal. sk_t is used to decrypt a content key. Since skt is stored in a mobile terminal, it is vulnerable to being leaked. To protect services from such key leakage, we add a function to control when and where skt can be used. To introduce such a restriction, we employ an ABE scheme. The system uses ABE to exchange certain secret data between broadcasters and subscribers through communication networks. This key management system is secure against key leakage and enables subscribers obtain pay-TV services their homes.