Cryptology ePrint Archive: Report 2019/1058

Privacy-preserving auditable token payments in a permissioned blockchain system

Elli Androulaki and Jan Camenisch and Angelo De Caro and Maria Dubovitskaya and Kaoutar Elkhiyaoui and Björn Tackmann

Abstract: Token management systems were the first application of blockchain technology and are still the most widely used one. Early implementations such as Bitcoin or Ethereum provide virtually no privacy beyond basic pseudonymity: all transactions are written in plain to the blockchain, which makes them perfectly linkable and traceable. Several more recent blockchain systems, such as Monero or Zerocash, implement improved levels of privacy. Most of these systems target the permissionless setting, just like Bitcoin. Many practical scenarios, in contrast, require token systems to be permissioned, binding the tokens to user identities instead of pseudonymous addresses, and also requiring auditing functionality in order to satisfy regulation such as AML/KYC. We present a privacy-preserving token management system that is designed for permissioned blockchain systems and supports fine-grained auditing. The scheme is secure under computational assumptions in bilinear groups, in the random-oracle model.

Category / Keywords: cryptographic protocols /

Date: received 17 Sep 2019, last revised 18 Oct 2019

Contact author: kao at zurich ibm com

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Version: 20191018:190109 (All versions of this report)

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