Microarchitecture Online Template Attacks
share
Online template attack (OTA) is a powerful technique previously used to attack elliptic curve scalar multiplication algorithms. This attack has been only analyzed in the realm of power-consumption and EM side-channels, where the signals leak about the value to be processed. However, no microarchitecture analysis variant has been proposed, especially considering the different nature between power-consumption signals and microarchitecture-based ones. In this paper we start filling this gap by revisiting the original OTA description, proposing a generic framework and evaluation metrics for any side-channel signal. Our analysis reveals OTA features not covered before, increasing its application scenarios that requires revisiting original countermeasures to prevent it. In this regard we demonstrate that OTA can work in the backward direction allowing to mount an augmented projective coordinates attack wrt the proposed by Naccache et al. (Eurocrypt 2004). We analyze three libraries libgcrypt, mbedTLS, and wolfSSL using two microarchitecture side-channels. For the libgcrypt case we target its EdDSA implementation using Curve25519 twist curve. We obtain similar results for mbedTLS and wolfSSL with curve secp256r1. For each library we execute extensive attack instances being able to recover the complete scalar in all cases using a single trace. In this work demonstrate that microarchitecture online template attacks are also very powerful in this scenario, recovering secret information without knowing a leakage model. This highlights the importance of developing secure-by-default implementations, instead of fix-on-demand ones.
READ FULL TEXT