AEP-M: Practical anonymous E-payment for mobile devices using ARM trustzone and divisible E-cash

Abstract

Electronic payment (e-payment) has been widely applied to electronic commerce and has especially attracted a large number of mobile users. However, current solutions often focus on protecting users’ money security without concerning the issue of users’ privacy leakage. In this paper, we propose AEP-M, a practical anonymous e-payment scheme specifically designed for mobile devices using TrustZone. On account of the limited resources on mobile devices and time constraints of elec- tronic transactions, we construct our scheme based on efficient divisible e-cash system. Precisely, AEP-M allows users to withdraw a large coin of value 2n at once, and then spend it in several times by dividing it without revealing users’ identities to others, including banks and mer- chants. Users’ payments cannot be linked either. AEP-M utilizes bit- decomposition technique and pre-computation to further increase the flexibility and efficiency of spending phase for mobile users. As a conse- quence, the frequent online spending process just needs at most n expo- nentiations on elliptic curve on mobile devices. Moreover, we elaborately adapt AEP-M to TrustZone architecture for the sake of protecting users’ money and critical data. The methods about key derivation and sensi- tive data management relying on a root of trust from SRAM Physical Unclonable Function (PUF) are presented. We implement a prototype system and evaluate AEP-M using Barreto-Naehrig (BN) curve with 128-bit security level. The security analysis and experimental results indicate that our scheme could meet the practical requirement of mobile users in respects of security and efficiency.