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CHIN-I LEE1, TZONG-CHEN WU1,2, BO-YIN YANG2 AND WEN-GUEY TZENG3
1Department of Information Management
National Taiwan University of Science and Technology
Taipei, 106 Taiwan
2Institute of Information Science
Academia Sinica
Taipei, 115 Taiwan
3Department of Computer Science
National Chiao Tung University
Hsinchu, 300 Taiwan
This paper proposes a new secure broadcasting scheme to realize the property of
¡§information granularity¡¨, wherein a receiver with a higher security clearance level has
the natural capability to recover a larger amount of information from the broadcasted
message block. Based on the intractability of the product of the l-weak Bilinear Diffie-Hellman Inversion problem and the n-modified Bilinear Diffie-Hellman problem, the
proposed scheme achieves the following features: (i) the length of the enabling block is
independent of the number of receivers and the number of security clearance levels; (ii)
each receiver holds only one small fixed-size decryption key corresponding to his/her
security clearance level; (iii) it is computationally feasible for any receiver to derive a
session key of a lower but never a higher security clearance level, even taking into account
collusion with other receivers; (iv) any receiver can dynamically join or leave the
system without resolving the re-keying problem for the existing receivers.
Received January 20, 2009; revised May 19, 2009; accepted June 30, 2009.
Communicated by Chin-Laung Lei.
* This work was sponsored in part by TWISC (Taiwan Information Security Center), National Science Council
under the grants NSC 96-2221-E-011-148-MY1 & MY2 and NSC 97-2219-E-001-001.