Enhanced key management for cable TV service

Cable TV service provider must manage the encryption/decryption keys to ensure that only the authorized set-top boxes can decrypt the pay-TV channels, and ITU recommended a key management scheme for this purpose. Nevertheless, some crackers crack and reproduce set-top boxes for profit, and many people use the pirated set-top boxes to decrypt and watch the pay-TV channels without paying subscription fee. In this paper, we enhance the key management scheme to protect the service provider's revenue against piracy. Using the enhanced scheme, even if a cracker could crack and reproduce set-top boxes, the pirated set-top boxes are only applicable in a small geographical region (i.e., they have limited spatial applicability) and they will not function within one charging period (i.e., they have limited temporal applicability).