New Secure Broadcasting Scheme Realizing Information Granularity

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 -weak Bilinear DiffieHellman 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.