OPERA: A Complete Offline and Anonymous Digital Cash Transaction System with a One-Time Readable Memory

Ki-Woong PARK  Sung Hoon BAEK  

IEICE TRANSACTIONS on Information and Systems   Vol.E100-D   No.10   pp.2348-2356
Publication Date: 2017/10/01
Online ISSN: 1745-1361
DOI: 10.1587/transinf.2016INP0008
Type of Manuscript: Special Section PAPER (Special Section on Security, Privacy and Anonymity in Computation, Communication and Storage Systems)
Category: Privacy, anonymity, and fundamental theory
offline digital payment,  digital cash,  

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Emerging digital payment services, also known as FinTech, have enabled various types of advanced payment transactions (such as Google Wallet, Apple Pay, Samsung Pay, etc.). However, offline peer-to-peer cash transactions still make up about 25.6% of the overall financial transactions in everyday life. By investigating existing online and offline payment systems, we identify three key challenges for building a digital cash transaction system with core features of the offline cash transactions: self-verifiability of digital cash; user anonymity; atomic cash transfer for double spending/depositing protection. In this paper, we propose OPERA, an offline peer-to-peer digital cash transaction system that addresses the three challenges. It newly introduces a concept of ‘one-time-readable memory(ORM)’ and ‘digital token’ which is a unit of self-verifiable digital cash. The one-time readability from ORM and three-stage token exchange protocol enable OPERA to provide uniqueness to digital cash and to allow a complete offline digital payment. OPERA devices are enhanced with TCPA technology to ensure the integrity of the physical device package. To evaluate the feasibility and resilience of the OPERA design, we built a prototype on a customized embedded board.