Critical Vulnerability CVE-2024-45678 (EUCLEAK) in YubiKey Hardware Security Tokens: A Threat Analysis for Bitcoin Cryptographic Security

The discovery of vulnerability CVE-2024-45678, known as EUCLEAK, in YubiKey Series 5 hardware security tokens represents one of the most significant cryptographic security incidents of the past decade. This vulnerability, which existed undetected for 14 years and has undergone approximately 80 top-level Common Criteria certifications, exposes critical flaws in the cryptographic library of Infineon Technologies, one of the largest secure element manufacturers in the world. This paper presents a comprehensive scientific analysis of the EUCLEAK attack mechanisms, its technical aspects, and its potential impact on the security of the Bitcoin cryptocurrency, including a detailed examination of electromagnetic side-channel attacks and their implications for modern cryptographic systems.

Technical nature of the CVE-2024-45678 vulnerability and attack classification

Electromagnetic Side-Channel Attack: Scientific Classification

The EUCLEAK vulnerability is an electromagnetic side -channel attack, which belongs to a class of passive physical attacks on cryptographic systems. In scientific literature, this type of attack is classified as a variant of TEMPEST attacks —the US National Security Agency’s codename for methods of intercepting unintentional electromagnetic emissions from electronic devices. More precisely, EUCLEAK belongs to a subcategory of Differential Electromagnetic Analysis (DEMA), which uses statistical methods to correlate electromagnetic emissions with cryptographic operations. arxiv+ 7

According to a systematic classification of side-channel attacks proposed in the modern scientific literature, EUCLEAK is characterized by the following parameters: it is a non-invasive attack (does not require opening the device for initial analysis), a local attack (requires physical proximity to the device), and exploits the timing characteristics of cryptographic operations, which are manifested through electromagnetic emissions. The attack exploits the non-constant-time execution of the modular inversion in the extended Euclidean algorithm, which creates an information leak through timing variations detected as changes in electromagnetic emissions. linkedin+ 5

Cryptographic Foundations of Vulnerability: ECDSA Algorithm and secp256k1

The EUCLEAK vulnerability affects the implementation of the Elliptic Curve Digital Signature Algorithm (ECDSA), a fundamental cryptographic primitive in the FIDO protocol and cryptocurrency systems, including Bitcoin. ECDSA exploits the mathematical properties of elliptic curves over finite fields to create digital signatures that provide authentication and data integrity. linkedin+ 5

In the context of Bitcoin, a specific elliptic curve, secp256k1 , defined by the Standards for Efficient Cryptography Group (SECG), is used. This curve is described by the equation $y^{2} = x^{3} + 7$ over a finite field $F_{p}$ , Where $p = 2^{256} - 2^{32} - 977$ — a prime number that determines the size of the field. The order of the group of points on this curve is $n \approx 2^{256}$ , which provides a 128-bit level of security against known cryptanalytic attacks. github+ 3

The ECDSA signature generation process includes the following steps: generation of an ephemeral random number (nonce) $k$ k , calculating a point on an elliptic curve $R = k \cdot G$ (Where $G$ — generating point), extraction of coordinate $r = x_{R} m o d n$ , and calculating the signature value $s = k^{- 1} (h + r \cdot d) m o d n$ n , where $h$ — the message hash, and $d$ — private key. The critical element is the modular inversion operation. $k^{- 1} m o d n$ , which in the vulnerable Infineon implementation executes with inconsistent timing. keysight+ 4

Extended Euclidean Algorithm and Time Leakage

The vulnerability is localized in the implementation of the Extended Euclidean Algorithm (EEA), used to calculate modular inverses. This algorithm calculates the greatest common divisor of two numbers and simultaneously finds the coefficients of the Bézout representation, allowing for the efficient calculation of multiplicative inverses in modular arithmetic. linkedin+ 5

NinjaLab researchers discovered that the EEA implementation in the Infineon cryptographic library exhibits data- dependent timing variations. Specifically, the number of algorithm iterations and the execution of conditional branches depend on the bit length and value of the number being inverted. $k$ k . These timing variations, measured with nanosecond precision , manifest themselves in the electromagnetic emissions characteristics of the microcontroller during cryptographic operations. keysight+ 3

Mathematically, EEA iteratively updates tuples of values $(r_{0}, r_{1}, s_{0}, s_{1}, t_{0}, t_{1})$ , where at each step, a modulo division and a conditional update of variables are performed. The time variability arises because: (1) the number of iterations depends on the bit length of the input data; (2) within each iteration, conditional operations are performed, the timing of which depends on the sign and magnitude of the intermediate values; (3) subtraction and comparison operations are performed a variable number of times. These time leaks create discernible patterns in the electromagnetic emanations, which can be detected and analyzed. arxiv+ 4

EUCLEAK attack methodology and technical requirements

Experimental setup and equipment

A successful EUCLEAK attack requires specialized equipment for recording electromagnetic radiation with high temporal resolution. NinjaLab researchers used a Langer EMV RF-B 3-2 electromagnetic probe (EM probe), an oscilloscope with a sampling rate of at least 1 million samples per second, and specialized signal processing software. The cost of the complete experimental setup, including a laptop for data analysis, is estimated at approximately $11,000 (approximately €10,000). keysight+ 6

Physical access to the device is a prerequisite for the attack. To obtain the clearest possible signal, an attacker must open the YubiKey or other vulnerable device’s casing to place an electromagnetic probe in close proximity to the Infineon SLE78 security microcontroller. While it is theoretically possible to attack through an intact casing using more sensitive equipment, this significantly complicates the process and reduces the signal-to-noise ratio. After data collection is complete, the device can be resealed and returned to the owner with no visible signs of compromise. linkedin+ 7

Key extraction process: theoretical and practical aspects

The EUCLEAK attack consists of several sequential stages. The first stage is the acquisition phase : the attacker must force the device to perform multiple ECDSA signature operations using the same private key while simultaneously recording electromagnetic emissions. Depending on the attacker’s skill and the system configuration, obtaining a sufficient number of traces requires anywhere from several minutes to an hour of physical access to the device. keysight+ 3

The second stage is offline analysis : the collected electromagnetic traces are subjected to complex statistical processing to extract information about the temporal characteristics of the modular inversion. The researchers used bandpass filtering, moving median analysis, and correlation analysis to identify patterns associated with specific bits of the ephemeral key. $k$ k . By analyzing the differences in the duration of individual EEA iterations, one can reconstruct the values of the algorithm’s intermediate variables, which gradually reveals the bits of the nonce $k$ k . arxiv+ 3

The third stage is private key recovery : after partial or complete recovery of the nonce $k$ k of one or more signatures, private key $d$ d can be calculated mathematically. From the equation of the signature $s = k^{- 1} (h + r \cdot d) m o d n$ it follows that $d = r^{- 1} (k \cdot s - h) m o d n$ d = r −1( k ⋅ s − h )mod n . If the nonce was recovered with errors, the researchers used Pollard’s Kangaroo algorithm to find the private key in a limited range of possible values. This algorithm for solving the discrete logarithm problem has a time complexity of $O (\sqrt{b - a})$ , Where $[a, b]$ — a known range, which makes it practical to use when partial information about the key is available. ninjalab+ 5

According to researchers, the offline analysis phase takes approximately 24 hours when the attack is initially implemented, but can be reduced to less than one hour with further optimization of the software and analysis methods. ninjalab+ 3

The scope of the vulnerability and affected devices

Yubico products and firmware versions

All YubiKey 5 Series devices with firmware prior to 5.7.0 are vulnerable to CVE-2024-45678. This includes the following models: YubiKey 5 NFC, YubiKey 5 Nano, YubiKey 5C, YubiKey 5C Nano, YubiKey 5Ci, and all variants of the YubiKey 5 FIPS Series with firmware prior to 5.7. Additionally, YubiKey Bio Series devices with firmware prior to 5.7.2 and Security Key Series devices with firmware prior to 5.7.0 are affected . YubiHSM 2 hardware security modules with firmware prior to 2.4.0 are also vulnerable. linkedin+ 3

It’s important to note that YubiKey device firmware cannot be updated by users. The firmware is installed during manufacturing and remains unchanged for the life of the device. Therefore, the only way to mitigate the vulnerability for users of older models is to physically replace the device with a new version running firmware 5.7.0 or higher. Updated versions, which began shipping on May 21, 2024 , use a new cryptographic library developed by Yubico, which does not contain the EUCLEAK vulnerability. reddit+ 6

Infineon Microcontrollers and Global Distribution

The vulnerability affects all Infineon security microcontrollers (MCUs ) that use the vulnerable Infineon cryptographic library. This includes the following product families: Trusted Platform Modules (TPMs) based on the Infineon Optiga TPM, the Infineon SLE78 series of secure elements , and the newer Infineon Optiga Trust M series . These MCUs are embedded in a wide range of devices, including hardware cryptocurrency wallets from various manufacturers, electronic passports, national ID cards, enhanced-security SIM cards, and smart home and car systems using ECDSA for authentication. linkedin+ 5

According to NinjaLab’s research, the vulnerability existed for over 14 years , since approximately 2010. During this period, the vulnerable cryptographic library passed approximately 80 top-level Common Criteria certification assessments : AVA_VAN.4 levels for TPM modules and AVA_VAN.5 for other protected elements. This demonstrates fundamental problems in the security certification process, where sophisticated side-channel attacks can remain undetected even by the most stringent assessments. ninjalab+ 6

Potential impact on Bitcoin security

Bitcoin Security Architecture and the Role of ECDSA

The Bitcoin cryptocurrency relies on the ECDSA algorithm with the secp256k1 curve as a fundamental cryptographic primitive for securing transactions and controlling ownership of digital assets. Each Bitcoin user generates a key pair: a private key $d$ d is a random 256-bit number from the range $[1, n - 1]$ , Where $n$ — the order of the group of points on secp256k1, and the public key $Q = d \cdot G$ , Where $G$ — a generating point of the curve. The public key is hashed to create a Bitcoin address to which funds can be sent. github+ 4

When making a transaction, the owner of the funds must create a digital signature proving possession of the private key corresponding to the sending address. This signature is generated using ECDSA and verified by Bitcoin network nodes to confirm the transaction’s legitimacy. Compromise of the private key means complete loss of control over all funds associated with the corresponding address, with no possibility of recovery. bitcoin+ 5

EUCLEAK Attack Scenarios for Bitcoin Wallets

The EUCLEAK vulnerability poses a serious threat to users of hardware cryptocurrency wallets built on vulnerable Infineon microcontrollers. While the specific wallet models affected by the attack have not been comprehensively tested, researchers indicate that any device using Infineon security microcontrollers with the vulnerable cryptographic library for ECDSA operations is potentially vulnerable. ninjalab+ 4

The attack scenario involves the following steps: (1) the attacker gains temporary physical access to the victim’s hardware wallet, such as through theft and return, interception during delivery, or insider trading; (2) the device is opened and an electromagnetic probe is placed to record signals during signature transactions; (3) the attacker initiates multiple transaction signatures, which may require knowledge of the device’s PIN, if set, or exploitation of additional vulnerabilities to bypass authentication; (4) once a sufficient number of electromagnetic traces have been collected, the device is resealed and returned to the owner; (5) the private key is extracted offline within 1-24 hours; (6) the attacker creates and signs a transaction transferring all funds from the compromised address to an address controlled by the attacker. reddit+ 8

Limitations of the attack’s practical application

Despite the theoretical seriousness of the threat, the practical application of the EUCLEAK attack against Bitcoin wallets faces several significant limitations. First, the attack requires physical access to the device for a period of several minutes to an hour, making it unsuitable for remote attacks. Second, the need for expensive specialized equipment (approximately $11,000) and high technical expertise in cryptography and electrical engineering significantly limits the pool of potential attackers. linkedin+ 8

Third, many modern hardware wallets require physical confirmation of transactions on the device and the entry of a PIN or biometric authentication. If these security mechanisms are implemented correctly, an attacker will not be able to force the device to perform signature transactions without knowing the PIN or bypassing biometrics, significantly complicating the data collection phase. Fourth, following the discovery of the vulnerability in September 2024, hardware wallet manufacturers began migrating to alternative secure elements or updated versions of Infineon microcontrollers with a patched cryptographic library. reddit+ 7

It’s also important to note that the vulnerability only affects signature operations performed on the vulnerable device. Bitcoin addresses created using other methods (such as software wallets based on BIP32/BIP39 deterministic hierarchical wallets running on devices without vulnerable Infineon microcontrollers) are not vulnerable to the EUCLEAK attack. Furthermore, the Bitcoin protocol itself and the ECDSA cryptographic algorithm remain secure—the vulnerability is related solely to the specific implementation of modular inversion in the Infineon cryptographic library. keysight+ 7

Context of other Bitcoin cryptographic vulnerabilities

The EUCLEAK vulnerability should be considered in the context of other known cryptographic issues affecting the security of Bitcoin private keys. One of the most serious historical issues was nonce reuse in ECDSA signatures. If two different messages are signed using the same ephemeral key, $k$ k , the private key can be trivially calculated from the two signatures by solving a system of linear equations modulo $n$ n . sciencedirect+ 3

A 2017 analysis of Bitcoin transactions by researchers found that approximately 0.48% of signatures were affected by the weak randomness issue, leading to the compromise of 1,331 private keys . This issue was partially mitigated by the introduction of RFC 6979 , a standard for deterministic nonce generation that eliminates the reliance on a random number generator and makes the signing process reproducible and free of nonce reuse. Most modern Bitcoin implementations, including Bitcoin Core, have adopted RFC 6979, significantly reducing the risk of key leakage through weak randomness. reddit+ 2

Another category of attacks includes lattice attacks and partial nonce disclosure attacks. If several bits of the nonce $k$ k leaks through various channels (e.g., timing attacks, side-channel attacks, or implementation bugs), a lattice structure can be constructed that allows the full private key to be recovered using the LLL (Lenstra–Lenstra–Lovász) algorithm or the Pollard kangaroo algorithm. EUCLEAK, by its nature, represents precisely this type of attack—partial disclosure of nonce information through timing characteristics manifested in electromagnetic emissions. keysight+ 5

Countermeasures and protection prospects

Software countermeasures: constant-time implementations

A fundamental defense against timing side-channel attacks, including EUCLEAK, is constant-time programming . This approach requires that the execution time of critical cryptographic operations be independent of the secret data values processed by the algorithm. In the context of ECDSA, this means that the operations of nonce generation, modular inversion, scalar multiplication on an elliptic curve, and the final signature computation must all execute in the same time, regardless of the bit values of the private key and the ephemeral key. arxiv+ 6

Various techniques can be used to achieve constant time in modular inversion. One approach is to use an algorithm based on Fermat’s little theorem : computing $k^{- 1} m o d n$ k −1mod n as $k^{n - 2} m o d n$ k n −2mod n using fast constant-time exponentiation. This method guarantees a fixed number of operations regardless of the value of $k$ k , but can be computationally more expensive than optimized variants of the extended Euclidean algorithm. An alternative approach is to create a constant-time version of the EEA , where all conditional jumps are replaced by arithmetic operations using masks, and the number of iterations is fixed and equal to the worst-case yp+ 2

Additional techniques include masking and blinding . Masking introduces random values that algebraically mask secret data throughout the computation and are then removed at the end, ensuring the correct result. For modular inversion, this might mean computing $(r \cdot k)^{- 1} m o d n$ ( r ⋅ k )−1mod n , where $r$ r is a random number and then multiply the result by $r$ r to receive $k^{- 1}$ k −1. Blinding the ephemeral key during signature computation can also effectively mask the timing characteristics from an attacker. gistre.epita+ 3

Hardware countermeasures and secure elements

At the hardware level, protection against electromagnetic side-channel attacks can include electromagnetic shielding of the microcontroller, the use of dual-rail logic that consumes constant power regardless of the data being processed, and noise injection into power and clock signals to mask information leaks. Faraday cages can effectively block electromagnetic radiation, but their practical application in small consumer devices like the YubiKey presents technological and economic challenges. halborn+ 6

Modern Secure Elements (SEs) and Hardware Security Modules (HSMs) are designed to withstand physical attacks. They include built-in countermeasures against power analysis, electromagnetic analysis, fault injection, and other forms of attack. Certification to Common Criteria EAL5+ or FIPS 140-2/140-3 Level 3+ requires demonstrating resistance to a wide range of side-channel attacks. However, as the EUCLEAK case demonstrates, even devices that have achieved the highest levels of certification can contain subtle vulnerabilities that are detectable using advanced analysis techniques. ninjalab+ 6

Architectural approaches in the Bitcoin ecosystem

From an architectural perspective, the Bitcoin ecosystem can employ several strategies to minimize the risks associated with side-channel attacks on hardware wallets. Multi-signature (multi-sig) configurations , where signatures from multiple independent keys stored on different devices or platforms are required to authorize a transaction, can significantly enhance security. Even if one key is compromised via an EUCLEAK attack, funds remain secure until the attacker gains access to a sufficient number of other keys. coinspect+ 3

Hierarchical Deterministic Wallets (HD wallets) comply with the BIP32/BIP39/BIP44 standards to generate multiple addresses from a single seed phrase. When implemented correctly, compromising one child key should not reveal the master key or other child keys. However, this depends on the use of hardened derivations , which provide cryptographic separation between keys. github+ 2

Temporary key rotation and limiting address reuse are best practices that also mitigate risks. If each Bitcoin address is used only once, and funds are regularly moved to new, independently generated addresses, the window of opportunity for an attacker to compromise a specific key is significantly reduced. It’s also important to upgrade hardware wallets to models with patched microcontrollers and use only devices from trusted manufacturers with transparent vulnerability disclosure and update processes. coolwallet+ 4

Conclusion: EUCLEAK’s Lessons for the Crypto Industry

The discovery of vulnerability CVE-2024-45678 in YubiKey hardware tokens and other devices based on Infineon microcontrollers represents an important precedent in the field of cryptographic security. The fact that this critical vulnerability remained undetected for 14 years and has undergone nearly 80 top-tier certifications demonstrates the fundamental limitations of current security assessment processes. This underscores the need for more rigorous testing methodologies specifically aimed at detecting subtle side-channel attacks, as well as the importance of continually reviewing and updating certification standards. linkedin+ 8

The scientific classification of EUCLEAK as an electromagnetic side-channel attack exploiting the variable execution time of the extended Euclidean algorithm fits into the broader context of research into the security of cryptographic implementations. This reminds the industry that theoretically secure cryptographic algorithms can be compromised through vulnerabilities in their practical implementations, especially when constant-time programming principles are not followed. arxiv+ 7

For the Bitcoin ecosystem, the threat posed by EUCLEAK is moderate, given the high barriers to attack: the need for physical access, expensive equipment, and technical expertise. However, users of hardware cryptocurrency wallets based on vulnerable Infineon microcontrollers should consider migrating to updated devices and implementing multi-layered security strategies, such as multi-signature and hierarchical deterministic wallets. reddit+ 7

More broadly, the EUCLEAK incident highlights the critical importance of transparency, responsible disclosure of vulnerabilities, and collaboration between security researchers, hardware manufacturers, software developers, and certification authorities. Only through such collaboration can the cryptographic industry effectively counter constantly evolving threats and ensure reliable protection of digital assets and personal data in today’s interconnected world. ninjalab+ 3