Abstract
Digital multimedia content is delivered to
homes via the Internet, satellite, terrestrial and cable networks.
Scrambling is a common approach used by conditional
access systems to prevent unauthorized access to audio/
visual data. The descrambling keys are securely distributed
to the receivers in the same transmission channel.
Their protection is an important part of the key management
problem. Although public-key cryptography provides
a viable solution, alternative methods are sought for economy
and emcieney.
Message authentication is an important objective of information
security in modern electronic distribution networks.
This objective is met by providing the receiver of a message
an assurance of the sender's identity. As physical protection
such as sealed envelopes is not possible for messages
expressed as binary sequences, digital tools have been developed
using cryptography, A major limitation of all cryp
tographic methods for message authentication lies in their
use of algorithms with flxed symmetric or public keys.
This paper presents a key transport protocol based on secret
sharing. Conditional access and message authentication
are two important application areas for which the advantages
of the proposed protocol are discussed. The protocol
eliminates the need for a cipher, yet effectively combines the
advantages of symmetric and public-key ciphers. It can be
used to build a new key management scheme that allows the
service providers to generate different keys for different sets
of receivers, and to renew these keys in a convenient way.