On the Security of Dynamic Group Signatures: Preventing Signature Hijacking

We identify a potential weakness in the standard security model for dynamic group signatures which appears to have been overlooked previously. More specifically, we highlight that even if a scheme provably meets the security requirements of the model, a malicious group member can potentially claim ownership of a group signature produced by an honest group member by forging a proof of ownership. This property leads to a number of vulnerabilities in scenarios in which dynamic group signatures are likely to be used. We furthermore show that the dynamic group signature scheme by Groth (ASIACRYPT 2007) does not provide protection against this type of malicious behavior. To address this, we introduce the notion of opening soundness for group signatures which essentially requires that it is infeasible to produce a proof of ownership of a valid group signature for any user except the original signer. We then show a relatively simple modification of the scheme by Groth which allows us to pro...

• Type: Journal
• Year: 2012
• Where: PKC
• Authors: Yusuke Sakai, Jacob C. N. Schuldt, Keita Emura, Goichiro Hanaoka, Kazuo Ohta
• Keywords: Cryptology, Dynamic Group, Group Signature Scheme, Group Signatures, PKC 2012