Paper 2022/872

Nirvana: Instant and Anonymous Payment-Guarantees

Akash Madhusudan, imec-COSIC, KU Leuven, Leuven, Belgium
Mahdi Sedaghat, imec-COSIC, KU Leuven, Leuven, Belgium
Philipp Jovanovic, University College London, London, UK
Bart Preneel, imec-COSIC, KU Leuven, Leuven, Belgium

Given the high transaction confirmation latencies in public blockchains, cryptocurrencies such as Bitcoin, Ethereum, etc. are not yet suitable to support real-time services such as transactions on retail markets. There are several solutions to address this latency problem, with layer-2 solutions being the most promising ones. Existing layer-2 solutions, however, suffer from privacy and/or collateral issues when applied to retail environments where customer-merchant relationships are usually ephemeral. In this paper, we propose Nirvana, that can be combined with existing cryptocurrencies to provide instant, anonymous and unlinkable payment guarantees. Nirvana does not require any trusted third party. It conceals the identities of honest participants, thus ensuring customer anonymity within the system while only relying on efficient Groth-Sahai proof systems. We introduce a novel randomness-reusable threshold encryption that mitigates double-spending by revealing the identities of malicious users. We formally prove how our scheme provides customer anonymity, unlinkability of transactions and payment guarantees to merchants. Our experiments demonstrate that Nirvana allows for fast (zero-confirmation) global payments in a retail setting with a delay of less than $1.7$ seconds.

Available format(s)
Cryptographic protocols
Publication info
Instant Payments Payment Guarantees Structure-Preserving Threshold Signature
Contact author(s)
akash madhusudan @ esat kuleuven be
ssedagha @ esat kuleuven be
p jovanovic @ ucl ac uk
bart preneel @ esat kuleuven be
2022-07-04: approved
2022-07-04: received
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Creative Commons Attribution


      author = {Akash Madhusudan and Mahdi Sedaghat and Philipp Jovanovic and Bart Preneel},
      title = {Nirvana: Instant and Anonymous Payment-Guarantees},
      howpublished = {Cryptology ePrint Archive, Paper 2022/872},
      year = {2022},
      note = {\url{}},
      url = {}
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