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 · 2017
Emerging digital payment services, also known as Fin-Tech, have enabled various types of advanced payment transactions (such as Google Wallet, Apple Pay, Samsung Pay, etc.).However, offline peerto-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.