Cryptology ePrint Archive: Report 2018/621

Cache-Attacks on the ARM TrustZone implementations of AES-256 and AES-256-GCM via GPU-based analysis

Ben Lapid and Avishai Wool

Abstract: The ARM TrustZone is a security extension which is used in recent Samsung flagship smartphones to create a Trusted Execution Environment (TEE) called a Secure World, which runs secure processes (Trustlets). The Samsung TEE includes cryptographic key storage and functions inside the Keymaster trustlet. The secret key used by the Keymaster trustlet is derived by a hardware device and is inaccessible to the Android OS. However, the ARM32 AES implementation used by the Keymaster is vulnerable to side channel cache-attacks. The Keymaster trustlet uses AES-256 in GCM mode, which makes mounting a cache attack against this target much harder. In this paper we show that it is possible to perform a successful cache attack against this AES implementation, in AES-256/GCM mode, using widely available hardware. Using a laptop's GPU to parallelize the analysis, we are able to extract a raw AES-256 key with 7 minutes of measurements and under a minute of analysis time and an AES-256/GCM key with 40 minutes of measurements and 30 minutes of analysis.

Category / Keywords: secret-key cryptography / side-channel, cache attacks

Date: received 20 Jun 2018

Contact author: yash at eng tau ac il

Available format(s): PDF | BibTeX Citation

Version: 20180622:145858 (All versions of this report)

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