We consider broadcast applications where the transmissions need to be encrypted, such as broadband digital TV networks or Internet multicasts. In these applications the number of encrypted TV programs may be very large, but the secure memory capacity at the set-top terminals (STT) is severely limited due to the need to withstand pirate attacks and hardware tampering. Despite this, we would like to allow the vendor to offer different packages of programs to the users. A user who buys a package should be able to view every program belonging to that package, but nothing else. A flexible scheme should allow for packages of various sizes to be offered, from a single program up to all the programs.
We suggest a novel scheme to manage the encryption keys for these
applications. The scheme is highly flexible, yet requires very few
keys to be stored in the STTs' secure memory. The computational
power required of the STTs is very low. The security of this scheme
is as good or better than that offered by current technology.
Paper Available at: ftp://dimacs.rutgers.edu/pub/dimacs/TechnicalReports/TechReports/1998/98-06.ps.gz