A simplified scheme for secure offline electronic payment systems

Abstract

This paper proposes a secure offline electronic (e-) payment scheme by adopting Schnorr's untraceable blind signature (BS). Thereby, to satisfy the essential security requirements of e-payment systems, it requires much more simple computations and becomes more practical than many existing schemes. Other considerations are: to prevent the forgery of e-coin, the Bank is only the lawful entity to produce the valid e-coin; and others can verify its correctness. To confirm no swindling, the e-coin owner also sticks her private signing key with the e-coin before spending it as the payment. Hence, through the commitment with challenge-response of Schnorr's BS, the merchant can verify the spent e-coin, and the trusted authority can identify the dishonest spender if multiple spending occurs. Moreover, it embeds three distinct information of date, namely expiration, deposit, and transaction dates with every e-coin. Thereby, it minimizes the size of the Bank's database, correctly calculates the interest of the e-coin, and helps in arbiter if multiple spending, respectively. Finally, it evaluates the performance and analyzes essential security requirements of the proposed scheme, plus studies a comparison with existing ones.

Keywords

• Offline electronic payment
• Schnorr's blind signature
• RSA algorithm
• Zero-knowledge proof
• Untraceability