Improving dm-crypt performance for XTS-AES mode through extended requests: first results

Levent Demir (1) , Mathieu Thiery (2) , Vincent Roca (1) , Jean-Louis Roch (3) , Jean-Michel Tenkes (2)

1 PRIVATICS - Privacy Models, Architectures and Tools for the Information Society
2 Chercheur indépendant
3 VERIMAG - IMAG - VERIMAG

Using dedicated hardware is common practice in order to accelerate cryptographic operations: complex operations are managed by a dedicated co-processor and RAM/crypto-engine data transfers are fully managed by DMA operations. The CPU is therefore free for other tasks, which is vital in embedded environments with limited CPU power. In this work we discuss and benchmark XTS-AES, using either software or mixed approaches, using Linux and dm-crypt, and a low-power At-mel(tm) board. This board featurs an AES crypto-engine that supports ECB-AES but not the XTS-AES mode. We show that the dm-crypt module used in Linux for full disk encryption has limitations that can be relaxed when considering larger block sizes. In particular we demonstrate that performance gains almost by a factor two are possible, which opens new opportunities for future use-cases.

Mots clés: DMA; scatterlist; linux kernel crypto API; decryption; atmel board; Full disk encryption; XTS-AES; encryption

Domaines: Cryptographie et sécurité [cs.CR]

Levent Demir, Mathieu Thiery, Vincent Roca, Jean-Louis Roch, Jean-Michel Tenkes. Improving dm-crypt performance for XTS-AES mode through extended requests: first results. GreHack 2016. The 4th International Symposium on Research in Grey-Hat Hacking - aka GreHack , Nov 2016, Grenoble, France. ⟨hal-01399967⟩