Post-Quantum Security: AI Discovers Vulnerability in One of the Candidates for New Digital Signatures

Post-quantum security has once again come into the spotlight following a statement from Anthropic: the Claude Mythos Preview model has identified a new variant of attack on the HAWK digital signature algorithm, which is being considered among potential tools for future post-quantum cryptography.

According to the company, the research took about 60 hours, and the computational costs amounted to approximately $100,000. The new method reduces the complexity of key searching for the least secure version of HAWK from about 2⁶⁴ to 2³⁸ operations.

More reliable key options remain resilient for now. However, this choice has a weak point: the algorithm almost loses its efficiency advantage. In other words, it may be safer, but it is no longer as convenient, which was the reason it was considered in the first place.

Why This Is Not a Direct Threat to Bitcoin and Ethereum This finding does not directly impact Bitcoin and Ethereum. These networks use a different type of signature—elliptic cryptography—and the experiment was not aimed at it. Their public key cryptosystem is structured differently: the electronic signature confirms the owner's right to manage the coins, while the public address does not reveal the private key (cryptography considers it the user's main secret).

However, the signal for the market is still significant: the development of AI accelerates the search not only for new protective solutions but also for attacks. For computer security, this means that promising encryption schemes and any new cipher will need to be tested more quickly and rigorously.

The longer a system needs to store secrets, the sooner it must prepare for a transition to post-quantum algorithms: data intercepted today may be attempted to be decrypted on more powerful computers tomorrow.

What Is Post-Quantum Security in Simple Terms Post-quantum security refers to the transition to cryptographic methods that must withstand attacks not only from conventional but also from future quantum computers. It is crucial for data that needs to be stored for years: financial transactions, government systems, cloud services, IoT devices, and secure communications.

Cryptographic protection is generally needed to hide data from outsiders, prevent unnoticed alterations, and confirm who exactly signed the message or operation. These are three basic tasks: confidentiality, integrity, and authentication.

What Are Post-Quantum Algorithms A post-quantum algorithm is an encryption or digital signature scheme designed to be resistant to quantum attacks. Such approaches include algorithms based on lattices, codes, polynomials, hash functions, and isogenies. HAWK is precisely among this group of candidates, although it is not currently used in Bitcoin.

Quantum encryption is a separate idea: it uses the properties of quantum particles to protect the channel, rather than just the complexity of a mathematical problem. In classical cryptography, security typically relies on the fact that it is practically impossible to guess the key; in the quantum approach, the very attempt to intercept the key unnoticed should leave a trace.

Where Quantum Risk Comes From The main danger discussed in the crypto industry is related to future quantum machines. If a sufficiently powerful quantum computer becomes a reality, it could theoretically compute private keys from known public ones. This poses a risk for many systems where the cryptosystem relies on the complexity of reverse computations.

At the core of such scenarios lies quantum mechanics, and in cryptography, the Shor algorithm is often mentioned: it is dangerous for schemes where security is tied to factorization or discrete logarithm problems. RSA, DSA, ECDSA, DH, and ElGamal rely on such problems, so with the emergence of sufficiently powerful quantum computers, electronic commerce, banking operations, secure communications, and services where signatures or key exchanges confirm trust could be at risk.

Bitcoin uses public keys for transactions. A similar logic applies to other cryptocurrencies and, to some extent, to banking applications. Therefore, post-quantum cryptography and the direction of PQC have become not just an abstract scientific topic but a practical issue for infrastructure.

How to Prepare for Quantum Threats

Preparation begins with an inventory: it is necessary to understand where signatures, key exchanges, and long-term storage of sensitive data are used. Then, it is advisable to monitor NIST and ISO standards, test post-quantum schemes in pilot systems, and build in cryptographic flexibility so that algorithms can be replaced without a complete overhaul of the infrastructure.

Practically, this means updating libraries, checking compatibility, planning migration of keys and addresses, as well as combined schemes for the transition period, where classical protection works alongside post-quantum.

What is Being Discussed for Bitcoin

Existing signatures may prove insufficient when powerful quantum computers emerge. Therefore, scientists are proactively developing new schemes designed to withstand quantum attacks. HAWK is one such backup option, but it is currently not in use, and there are no plans to implement it in Bitcoin.

• BIP-360 - a plan to transition to quantum-resistant addresses. It includes several algorithms to choose from: if one option is compromised, the network can switch to another.
• BIP-361 - the idea of freezing more than a third of all Bitcoin that resides on old and most vulnerable addresses. The authors believe that time is running out, as even classical, non-quantum attacks are accelerating 20 times due to the development of AI.

Although the quantum threat remains theoretical for now, it is already changing the market. The industry is implementing protective mechanisms and post-quantum solutions in crypto projects, and key players are directing tens of millions of dollars toward this. Some blockchain networks have already moved from discussions to practical adjustments of new algorithms.

Against this backdrop, attention to standards and key protection is only increasing:

• NIST is developing standards for post-quantum cryptography and setting benchmarks for the industry.
• IBM and other technology companies are investing in quantum technologies.
• Key protection is becoming part of national-level cybersecurity, including in the logic of cyber warfare.