Breaking ECDSA with Electromagnetic Side-Channel Attacks: Challenges and Practicality on Modern Smartphones

TL;DR

This paper demonstrates electromagnetic side-channel attacks can recover ECDSA keys on modern smartphones, revealing vulnerabilities in current cryptographic implementations and emphasizing the need for certified secure elements.

Contribution

It introduces new attack methodologies tailored to modern smartphone SoCs and evaluates their effectiveness on real devices, highlighting security weaknesses in current implementations.

Findings

ECDSA secrets can be recovered from Raspberry Pi 4 and Fairphone 4.

Libgcrypt countermeasure does not fully prevent EM SCA attacks.

Weaknesses in Android cryptographic implementations are identified.

Abstract

Smartphones handle sensitive tasks such as messaging and payment and may soon support critical electronic identification through initiatives such as the European Digital Identity (EUDI) wallet, currently under development. Yet the susceptibility of modern smartphones to physical side-channel analysis (SCA) is underexplored, with recent work limited to pre-2019 hardware. Since then, smartphone system on chip (SoC) platforms have grown more complex, with heterogeneous processor clusters, sub 10 nm nodes, and frequencies over 2 GHz, potentially complicating SCA. In this paper, we assess the feasibility of electromagnetic (EM) SCA on a Raspberry Pi 4, featuring a Broadcom BCM2711 SoC and a Fairphone 4 featuring a Snapdragon 750G 5G SoC. Using new attack methodologies tailored to modern SoCs, we recover ECDSA secrets from OpenSSL by mounting the Nonce@Once attack of Alam et al. (Euro S&P 2021) and show that the libgcrypt countermeasure does not fully mitigate it. We present case studies illustrating how hardware and software stacks impact EM SCA feasibility. Motivated by use cases such as the EUDI wallet, we survey Android cryptographic implementations and define representative threat models to assess the attack. Our findings show weaknesses in ECDSA software implementations and underscore the need for independently certified secure elements (SEs) in all smartphones.