EUCLEAK Side-Channel Attack on the YubiKey 5 Series
Researchers have demonstrated a side‑channel attack, dubbed EUCLEAK, that can extract private ECDSA keys from YubiKey 5 Series devices (firmware <5.7) and other Infineon‑based secure elements by measuring electromagnetic emissions from non‑constant‑time cryptographic operations. Commenters note that the exploit requires physical access, device disassembly, and lab‑grade equipment, so it mainly raises concerns for high‑value targets rather than typical users, but it also undermines FIDO2 attestation and “always‑verify” configurations. Much of the debate centers on Yubico’s non‑upgradable firmware, the absence (so far) of a broad replacement program despite past precedents, and the broader impact on passports, TPMs, hardware wallets, and other systems using the same Infineon crypto library.
Website & Resources
- Several people report the Ninjalab site hanging; workarounds include reader mode, blocking the loading overlay, or using the linked PDF.
- Links to Yubico’s advisory and support article are shared.
Vulnerability Scope & Requirements
- Affects YubiKey 5 series with firmware <5.7 using Infineon’s cryptographic library.
- Exploit is an electromagnetic side-channel on a non-constant-time modular inversion in ECDSA.
- Requires physical access, disassembly of the key, lab-grade EM equipment, and a few minutes of traces.
- Once refined, the attack might not require fully destroying the device; current work didn’t focus on re-packaging.
Impact on Security Guarantees
- Key extraction turns the device from “unextractable secrets” into “very hard-to-extract secrets”.
- Some argue this is mainly a high-end, targeted attack; others note many YubiKey use cases (crypto, defense, banking) are exactly such high-value targets.
- Attestation keys can also be cloned, undermining hardware model enforcement and FIDO attestation in some deployments.
Firmware, Mitigations & Replacement Debate
- YubiKey firmware is not upgradable; old devices remain vulnerable.
- Earlier Infineon issue (ROCA) led to free replacements; several posters are surprised replacements aren’t offered now.
- YubiKey 5.7 switches from Infineon to Yubico’s own crypto library; some are nervous about custom crypto, others say it’s reasonable after multiple vendor failures.
Broader Infineon Ecosystem
- Discussion notes all Infineon secure microcontrollers using the affected crypto library may be vulnerable: TPMs, e-passports, phone secure enclaves, SIMs, some hardware wallets, EMV cards, tachographs, etc.
- There’s debate about how serious this is for each: some see primarily forensic/government use; others highlight passports, banking apps, and payment systems as significant.
FIDO2, PINs, UV & Passkeys
- PIN/user verification can often be bypassed because relying parties may request “user verification not required”; thus the side-channel can be driven without PIN knowledge.
- This can reduce “key + PIN” from two factors to effectively one (possession).
- Resident (discoverable) vs non-resident credentials matter: resident ones can be attacked offline; non-resident need the credential ID, typically learned via a legitimate challenge.
Usability, Backups & Account Management
- Major pain point: no easy way to enumerate where a key is registered; users resort to tagging entries in password managers.
- Many recommend registering multiple keys only on critical services (email, password manager, SSO, cloud) and keeping backups in separate locations.
- Some lament difficulty of securely backing up or cloning keys; proposals for paired/synchronizable keys are debated as too risky/complex.
Crypto Engineering & Certification Critique
- Infineon is criticized for a non-constant-time primitive; modular inversion leaks are seen as a basic failure.
- Common Criteria certifications are questioned since the flaw survived ~14 years and many evaluations.
- Some note this is a known class of attacks; constant-time algorithms, blinding, or using schemes like EdDSA could have mitigated it.