Secret-public storage trade-off for broadcast encryption key management

Abstract

The problem of minimizing the amount of secret information (secret bits) required for certain key management schemes is addressed. It is important to note that the secret storage minimization originates from the fact that this storage should be both read-proof and tamper-proof. The proposed minimization of the secret storage at the user's side is based on an appropriate trade-off between the required public storage and the processing complexity. As the main components, two methods are proposed for assigning multiple roles to the same secret key bits, and both of them require only simple operations implying a high implementation efficiency. The first proposed one-way mapping is based on certain sequence comparison issues and the second one follows the model of a communication channel with erasures. Employment of a proposed mapping method in two computationally secure key management schemes for the broadcast encryption SD and LSD is considered and the modified versions of these schemes with minimized secret storage requirements are proposed. The main overheads of the original and the modified SD and LSD based schemes are compared and the advantages of the modified schemes are pointed out. Also, it is shown that the proposed secret to public storage exchange preserves the security of the original SD and LSD schemes.