single encryption key. All receivers can receive the encrypted messages
sent protected by the broadcast key.
How can the broadcast key itself be protected? How can it be changed
for most receivers but not others? How can subscribers to a premium
broadcast service be managed efficiently?
If hundreds of receivers are subscribed and one of them needs to be
excluded, a new broadcast key can be sent to each of the receivers
(encrypted on a key unique to each receiver), resulting in hundreds of
transmissions.
JigSaw Key breaks a new broadcast key into parts and delivers the
pieces securely to only the right receivers. An excluded receiver does not
receive all the pieces.
Receivers have a unique set of keys from a fairly small repertoire, like 16
from 32. Pieces are encrypted on several of the 32 keys for delivery to
groups of receivers. Only 1 piece is created for each excluded receiver.
