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Summary: IEEE/ACM TRANSACTIONS ON NETWORKING, VOL. 8, NO. 4, AUGUST 2000 443
Key Management for Restricted Multicast
Using Broadcast Encryption
Michel Abdalla, Student Member, IEEE, Yuval Shavitt, Member, IEEE, and Avishai Wool, Member, IEEE
Abstract--The problem we address is how to communicate se-
curely with a set of users (the target set) over an insecure broadcast
channel. This problem occurs in two application domains: satel-
lite/cable pay TV and the Internet MBone. In these systems, the
parameters of major concern are the number of key transmissions
and the number of keys held by each receiver. In the Internet do-
main, previous schemes suggest building a separate key tree for
each multicast program, thus incurring a setup cost of at least
log per program for target sets of size . In the pay-TV do-
main, a single key structure is used for all programs, but known
theoretical bounds show that either very long transmissions are
required, or that each receiver needs to keep prohibitively many
keys.
Our approach is targeted at both domains. Our schemes main-
tain a single key structure that requires each receiver to keep only
a logarithmic number of establishment keys for its entire lifetime.
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