OCRAM-Assisted Sensitive Data Protection on ARM-Based Platform

Abstract

On mobile devices, security-sensitive tasks (e.g., mobile payment, one-time password) involve not only sensitive data such as cryptographic keying material, but also sensitive I/O operations such as inputting PIN code via touchscreen and showing the authentication verification code on the display. Therefore, a comprehensive protection of these services should enforce a Trusted User Interface (TUI) to protect the sensitive user inputs and system outputs, in addition to preventing both software attacks and physical memory disclosure attacks. In this paper, we present an On-Chip RAM (OCRAM) assisted sensitive data protection mechanism named Oath on ARM-based platform to protect the sensitive data, particularly, sensitive I/O data, against both software attacks and physical memory disclosure attacks. The basic idea is to store and process the sensitive data in the OCRAM that is only accessible to the TrustZone secure world. After figuring out how to enable TrustZone protection for iRAM, we develop a trusted user interface with an OCRAM allocation mechanism to efficiently share the OCRAM between the secure OS and the rich OS. A prototype implemented on the OP-TEE system shows that Oath works well and has a small system overhead.