Omniring: Scaling private payments without trusted setup: Formal foundations and a construction of ring confidential transactions with log-size proofs

Lai RWF, Schröder D, Ronge V, Thyagarajan SAK, Ruffing T, Wang J (2019)

Publication Type: Conference contribution

Publication year: 2019

Publisher: Association for Computing Machinery

Pages Range: 31-48

Conference Proceedings Title: Proceedings of the ACM Conference on Computer and Communications Security

Event location: London GB

ISBN: 9781450367479

DOI: 10.1145/3319535.3345655

Abstract

Monero is the largest cryptocurrency with built-in cryptographic privacy features. The transactions are authenticated using zero-knowledge spend proofs, which provide a certain level of anonymity by hiding the source accounts from which the funds are sent among a set of other accounts. Due to its similarities to ring signatures, this core cryptographic component is called Ring Confidential Transactions (RingCT). Because of its practical relevance, several works attempt to analyze the security of RingCT. Since RingCT is rather complex, most of them are either informal, miss fundamental functionalities, or introduce undesirable trusted setup assumptions. Regarding efficiency, Monero currently deploys a scheme in which the size of the spend proof is linear in the ring size. This limits the ring size to only a few accounts, which in turn limits the acquired anonymity significantly and facilitates de-anonymization attacks. As a solution to these problems, we present the first rigorous formalization of RingCT as a cryptographic primitive. We then propose a generic construction of RingCT and prove it secure in our formal security model. By instantiating our generic construction with new efficient zero-knowledge proofs, we obtain Omniring, a fully-fledged RingCT scheme in the discrete logarithm setting that provides the highest concrete and asymptotic efficiency as of today. Omniring is the first RingCT scheme which 1) does not require a trusted setup or pairing-friendly elliptic curves, 2) has a proof size logarithmic in the size of the ring, and 3) allows to share the same ring between all source accounts in a transaction, thereby enabling significantly improved privacy level without sacrificing performance. Our zero-knowledge proofs rely on novel enhancements to the Bulletproofs framework (S&P 2018), which we believe are of independent interest.

Authors with CRIS profile

Wai Fu Lai Lehrstuhl für Informatik 13 (Angewandte Kryptographie) Dominique Schröder Lehrstuhl für Informatik 13 (Angewandte Kryptographie) Viktoria Ronge Lehrstuhl für Informatik 13 (Angewandte Kryptographie) Sri Aravinda Krishnan Thyagarajan Lehrstuhl für Informatik 13 (Angewandte Kryptographie)

Additional Organisation(s)

Graduiertenkolleg 2475 Cyberkriminalität und Forensische Informatik

Related research project(s)

Cyberkriminalität und forensische Informatik (Cybercrime) Oct. 1, 2019 - March 31, 2024

Involved external institutions

The Chinese University of Hong Kong (CUHK) CN China (CN) Blockstream CA Canada (CA)

How to cite

APA:

Lai, R.W.F., Schröder, D., Ronge, V., Thyagarajan, S.A.K., Ruffing, T., & Wang, J. (2019). Omniring: Scaling private payments without trusted setup: Formal foundations and a construction of ring confidential transactions with log-size proofs. In Proceedings of the ACM Conference on Computer and Communications Security (pp. 31-48). London, GB: Association for Computing Machinery.

MLA:

Lai, Russell W. F., et al. "Omniring: Scaling private payments without trusted setup: Formal foundations and a construction of ring confidential transactions with log-size proofs." Proceedings of the 26th ACM SIGSAC Conference on Computer and Communications Security, CCS 2019, London Association for Computing Machinery, 2019. 31-48.

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