Cybersecurity researchers at NinjaLab have uncovered a critical vulnerability in Infineon’s cryptographic library, used in numerous secure microcontrollers. This side-channel attack, dubbed EUCLEAK, has far-reaching implications for a wide range of products, including hardware security keys, electronic passports, and even smart cars.
Understanding EUCLEAK: A Threat to Cryptographic Security
EUCLEAK exploits a weakness in the implementation of the Extended Euclidean algorithm within Infineon’s cryptographic library. This vulnerability allows attackers with physical access to extract private keys from devices using Infineon’s solutions, effectively compromising their security.
The attack targets the time variation in modular inversion operations related to the Elliptic Curve Digital Signature Algorithm (ECDSA). Infineon’s library failed to implement constant-time execution for these operations, a common protection against side-channel attacks.
Widespread Impact: From YubiKeys to Smart Cars
The vulnerability affects a broad spectrum of products utilizing Infineon’s secure microcontrollers, including:
- YubiKey hardware security keys
- Trusted Platform Modules (TPMs)
- Electronic passports
- Feitian access cards
- Cryptocurrency wallets
- Smart car systems
Researchers have confirmed that all YubiKey 5 series models are vulnerable to cloning through this attack. However, the full extent of affected devices using the vulnerable microcontroller (such as Infineon SLE78, Optiga Trust M, and Optiga TPM) remains unknown.
The Anatomy of the EUCLEAK Attack
To execute the EUCLEAK attack, adversaries need physical access to the target device and specialized equipment worth approximately $11,000. The attack process involves:
- Gaining physical access to the device
- Using an oscilloscope to measure electromagnetic emissions during token authentication
- Analyzing timing differences to reveal the ECDSA ephemeral key (nonce)
- Extracting the ECDSA secret key through further analysis
While the attack requires sophisticated knowledge in electrical engineering and cryptography, it poses a significant threat in targeted scenarios, potentially compromising the core security of affected devices.
Implications for FIDO-Compatible Keys
The EUCLEAK attack undermines a fundamental security principle of FIDO-compatible keys: the inability to read or copy secret cryptographic material. This has severe implications for high-security environments, such as military and corporate networks, where these keys are widely used.
Mitigation and Industry Response
Yubico, the manufacturer of YubiKey, has acknowledged the vulnerability and released a security bulletin. All YubiKey devices with firmware versions prior to 5.7 (released in May 2024) are affected. Unfortunately, YubiKey firmware cannot be updated, leaving affected devices permanently vulnerable.
Infineon, the root cause of the vulnerability, has yet to provide an official statement. The full scope of affected devices beyond YubiKeys remains unclear, highlighting the need for a comprehensive industry response.
As the cybersecurity community grapples with the implications of EUCLEAK, it serves as a stark reminder of the ongoing challenges in securing cryptographic implementations. Organizations and individuals relying on potentially affected devices should reassess their security strategies and consider alternative solutions where possible. The incident underscores the critical importance of constant vigilance and third-party security audits in maintaining robust cybersecurity defenses.
