Hierarchical CRGK Supporting a Secure Multicast Communication for a Large Number of Users

Jihyun PARK  Jeongsu LEE  Jeonghyun KIM  Jaecheol RYOU  

IEICE TRANSACTIONS on Communications   Vol.E93-B   No.4   pp.862-870
Publication Date: 2010/04/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E93.B.862
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Fundamental Theories for Communications
group key management,  re-keying,  Chinese remainder theorem,  multicast,  broadcast,  

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A multicast content service, including numerous devices, requires an efficient group key management scheme as one of its core components. The purpose of group key management is to provide a secure key-sharing scheme among the members of a group so that messages transmitted via broadcasting or multicasting are not exposed to non-members. The Chinese Remaindering Group Key (CRGK) is an efficient group key management scheme based on the Chinese Remainder Theorem (CRT). It optimizes the number of re-key messages, the user-side key computation cost, and the number of stored keys. However, CRGK is not fit for a group with a large number of members because of the high computation complexity of the CRT. In this paper, we propose a Hierarchical CRGK (HCRGK) scheme that supports a group with a large number of members. We improved CRGK by adopting it to include an n-ary tree structure. The tree approach simplifies the group key management by distributing the group key computation to subgroups. Our scheme requires at most (log m N + 1) re-key messages for a group with N members and a short computation time even when the group is very large.