Cryptology ePrint Archive: Report 2007/354

Identity-Committable Signatures and Their Extension to Group-Oriented Ring Signatures

Cheng-Kang Chu and Wen-Guey Tzeng

Abstract: The identity of "Deep Throat", a pseudonym of the information source in the Watergate scandal, remained mysterious for more than three decades. In 2005, an ex-FBI official claimed that he was the anonymous source. Nevertheless, some are still inconvinced. In this paper, we introduce a new notion of identity-committable signatures (ICS) to ensure the anonymity of "Deep Throat" inside a group. A member of an organization can sign a message on behalf of himself (regular signature) or the organization (identity-committed signature). In the latter case, the signer's identity is hidden from anyone, and can be opened by himself only. We describe the requirements of ICS and give the formal definition of it. Then we extend the notion of ICS to group-oriented ring signatures (GRS) which further allow the signer to hide his identity behind multiple groups. We believe a GRS scheme is more efficient and practical than a ring signature scheme for leaking secrets. Finally, we provide concrete constructions of ICS and GRS with information-theoretic anonymity, that is, the identity of the signer is fully-protected.

Category / Keywords: public-key cryptography / Group Signatures, Ring Signatures

Publication Info: Full paper of an extended abstract that appeared at ACISP 2007.

Date: received 6 Sep 2007

Contact author: ckchu at cs nctu edu tw

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Version: 20070913:193643 (All versions of this report)

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