Key Management for Encrypted broadcast
We consider broadcast apphcations where the transmissions need to be encrypted, such as direct broadc-t digitd TV networks or Internet mtdticasts. In these apphcations the number of encrypted TV programs may be very large, but the secure memory capacity at the set-top termin~ (S~) is severely Lmited due to the need to withstand pirate attacks and hardware tampering. Despite this, we wotid fike to dow the vendor to offer different pa~ges of programs to the users. A user who buys a package shotid be able to view every program belonging to that package, but nothing eke. A flexible scheme shodd flow for packages of various sizes to be offered, from a single program up to M the programs. We suggest a novel scheme to manage the encryption keys for these app~cations. The scheme is higtiy flexible, yet requiresvery few keys to be stored in the STTS’ secure memory. The comput ation~ power required of the S~s is very low. The security of this scheme is as good or better than that offered by current technology.