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Authors: Lipmaa, Helger | Zhang, Bingsheng

Article Type: Research Article

Abstract: We propose a new non-interactive perfect zero-knowledge (NIZK) shuffle argument that, when compared with the only previously known efficient NIZK shuffle argument by Groth and Lu, has a small constant factor times smaller computation and communication, and is based on more standard computational assumptions. Differently from Groth and Lu who only prove the co-soundness of their argument under purely computational assumptions, we prove computational soundness under a necessary knowledge assumption. We also present a general transformation that results in a shuffle argument that has a quadratically smaller common reference string (CRS) and a small constant factor times longer argument than …the original shuffle. This can be interpreted as a general technique of decreasing the offline cost of an arbitrary shuffle argument. Show more

Keywords: Bilinear pairings, Clos network, cryptographic shuffle, non-interactive zero-knowledge, progression-free sets

DOI: 10.3233/JCS-130478

Citation: Journal of Computer Security, vol. 21, no. 5, pp. 685-719, 2013

Authors: Buldas, Ahto | Laud, Peeter | Lipmaa, Helger

Article Type: Research Article

Abstract: This paper presents a method to increase the accountability of certificate management by making it intractable for the certification authority (CA) to create contradictory statements about the validity of a certificate. The core of the method is a new primitive, undeniable attester, that allows someone to commit to some set S of bitstrings by publishing a short digest of S and to give attestations for any x that it is or is not a member of S . Such an attestation can be verified by obtaining in authenticated way the published digest and applying a verification algorithm to the triple …of the bitstring, the attestation and the digest. The most important feature of this primitive is intractability of creating two contradictory proofs for the same candidate element x and digest. We give an efficient construction for undeniable attesters based on authenticated search trees. We show that the construction also applies to sets of more structured elements. We also show that undeniable attesters exist iff collision-resistant hash functions exist. Show more

Keywords: Accountable certificate management, authenticated search trees, attesters, long-term authenticity, non-repudiation, public-key infrastructure, search trees, time-stamping

DOI: 10.3233/JCS-2002-10304

Citation: Journal of Computer Security, vol. 10, no. 3, pp. 273-296, 2002