Efficient page-cache encryption for smart devices with non-volatile main memory

Abstract

Since smart devices such as smart phones and tablets are at high risk of theft, they prevent information leakage from storage by full disk encryption (FDE). Recently, however, information leakage from memory is being critical as non-volatile main memory (NVMM) is emerging. In smart devices with NVMM, even if storage is encrypted, sensitive data in the page cache can be stolen by physical attacks. In this paper, we propose efficient page-cache encryption called Cache-Crypt to prevent part of the storage data from leaking via the page cache. Cache-Crypt is well integrated with FDE to avoid redundant cryptographic operations and take advantage of FDE. It bypasses encryption and decryption by FDE and stores encrypted data in the page cache. In response to application's requests, it executes encryption and decryption using FDE's cryptographic mechanism. To reduce the overhead, Cache-Crypt defers re-encryption of decrypted data temporarily. We have implemented Cache-Crypt in Linux and confirmed that the performance was comparable to that in FDE only.