A Flexible Method for Masked Sharing of Group Keys


IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E84-A   No.1   pp.239-246
Publication Date: 2001/01/01
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Cryptography and Information Security)
broadcast encryption,  user exclusion problem,  

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This paper proposes a group key distribution scheme with a user exclusion. The user exclusion is how to distribute an encryption key over a broadcast channel shared by n users so that all but d excluded users can get the group key. In the broadcast channel such as Pay-TV, Internet multicast and a mobile telecommunication for a group, a manager should exclude a dishonest user or an unauthorized terminal as soon as possible to protect the secrecy of the group communication. However, it takes a long time for the user exclusion on a large group, if the distributor distributes the group key to each user except the excluded one. We propose a scheme in which the amount of transmission and the key storage of each user do not depend on the number of users of the group. Moreover, our scheme does not require a fixed and privileged distributor.