Cryptology ePrint Archive: Report 2008/112

Democratic Group Signatures with Threshold Traceability

Dong Zheng and Xiangxue Li and Changshe Ma and Kefei Chen and Jianhua Li

Abstract: Recently, democratic group signatures(DGSs) particularly catch our attention due to their great flexibilities, \emph{i.e}., \emph{no group manager}, \emph{anonymity}, and \emph{individual traceability}. In existing DGS schemes, individual traceability says that any member in the group can reveal the actual signer's identity from a given signature. In this paper, we formally describe the definition of DGS, revisit its security notions by strengthening the requirement for the property of traceability, and present a concrete DGS construction with $(t, n)$-\emph{threshold traceability} which combines the concepts of group signatures and of threshold cryptography. The idea behind the $(t, n)$-threshold traceability is to distribute between $n$ group members the capability of tracing the actual signer such that any subset of not less than $t$ members can jointly reconstruct a secret and reveal the identity of the signer while preserving security even in the presence of an active adversary which can corrupt up to $t-1$ group members.

Category / Keywords: public-key cryptography / democratic group signature, anonymity, traceability,threshold traceability

Date: received 12 Mar 2008, last revised 16 Mar 2008

Contact author: xxli at sjtu edu cn

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Version: 20080316:142126 (All versions of this report)

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