AI Cracked a Crypto Algorithm in 60 Hours That Stumped Humans for Two Years

An AI model just cracked a cryptographic algorithm that survived two years of expert human review in just 60 hours, and the implications for Bitcoin and the entire crypto ecosystem are profound.

By Keisha Williams | July 30, 2026

The Hook

Anthropic, the AI company behind the Claude assistant, announced this week that its Claude Mythos Preview model discovered a serious flaw in HAWK, a proposed post-quantum digital signature scheme that was being considered as a replacement for the cryptographic tools that currently protect online banking, web payments, and — eventually — cryptocurrency transactions.

The AI-driven attack took roughly 60 hours and about 100,000 USD in computing costs. It effectively halved the smallest key strength of HAWK, reducing the work needed to break it from approximately 2^64 operations down to 2^38 operations. For context, that is the difference between “practically impossible to crack” and “theoretically within reach for a well-funded attacker.” HAWK had survived two years and two rounds of expert human review before the AI found what humans could not.

On-Chain Evidence

Digital signatures are the invisible foundation of cryptocurrency. Every time you send Bitcoin, the network verifies your right to spend those coins using a digital signature scheme. Every time Ethereum processes a smart contract transaction, signatures prove who authorized it. These cryptographic tools also protect every website showing a padlock icon in your browser — they are the plumbing beneath the entire digital economy.

The signature schemes used today by Bitcoin and Ethereum are expected to eventually fall to quantum computers. That is why organizations like the National Institute of Standards and Technology (NIST) have been running multi-year competitions to select new “post-quantum” algorithms — including HAWK — that can withstand attacks from both classical and quantum computers.

Anthropic’s AI did not break Bitcoin or Ethereum directly. Both networks currently use elliptic curve signatures, which neither the HAWK attack nor the AES improvements directly targeted. HAWK has not been deployed anywhere in production. But the speed and efficiency of the AI-driven attack sent a clear warning: the cryptographic assumptions underpinning digital assets are eroding faster than anyone expected.

The Core Conflict

The timing of Anthropic’s discovery is jarring for the crypto world. BIP-360, the proposal to give Bitcoin quantum-resistant addresses, specifies three algorithms NIST has already standardized, with multiple options included deliberately so users have fallbacks if one is later broken. BIP-361, the companion proposal that would freeze vulnerable coins — potentially more than a third of Bitcoin’s supply — argues that the migration window is closing because cryptographic attacks are improving by up to 20-fold.

Anthropic’s results align with that trend perfectly. What took human cryptanalysts years to evaluate, an AI model accomplished in days. And it is not just HAWK. The same Claude model produced improvements against a deliberately weakened version of AES — the cipher used to encrypt wallet files across the industry — by factors of 200 to 800. It also found smaller improvements, under tenfold, against Poseidon, the hash function that secures many zero-knowledge proof systems used in rollups and privacy protocols.

The privacy network Zcash activated its Ironwood upgrade just this week, introducing a new shielded pool designed to remain secure even if quantum computers arrive. The upgrade retires the old Orchard pool, where a counterfeiting bug sat undetected for four years. Every coin in Zcash’s roughly 80 million USD new Ironwood pool must now exit through gates that cap withdrawals at verified deposits — a direct response to the kind of existential cryptographic risks Anthropic’s research highlights.

Market Implications

For everyday crypto investors, the practical concern is not that an AI will break Bitcoin tomorrow. It will not. The real question is whether the Bitcoin and Ethereum communities can upgrade their cryptographic foundations fast enough to stay ahead of both quantum computers and AI-assisted classical attacks. The BIP-360 and BIP-361 proposals show that Bitcoin developers are taking the threat seriously, but consensus in a decentralized network is slow by design.

Investors holding coins in addresses generated years ago — including the estimated 1.1 million Bitcoin believed to be held by Satoshi Nakamoto — face the greatest exposure. Those early addresses use signature schemes that would be first to fall if a sufficiently powerful quantum computer comes online before the network upgrades. BIP-361 would allow the community to freeze those vulnerable coins, but that raises profound questions about who gets to decide which coins are “abandoned” and which are simply held long-term.

For projects building on zero-knowledge proofs — including Ethereum rollups, privacy coins, and identity systems — the Poseidon improvements are a reminder that even cutting-edge cryptography is not immune. Developers relying on ZK proofs for billions of dollars in daily transactions need to monitor these developments closely and be prepared to rotate to alternative hash functions if the attacks improve further.

The Verdict

Anthropic’s discovery is a wake-up call wrapped in good news. The attack on HAWK was found through responsible disclosure — Anthropic notified the algorithm’s authors in June and coordinated publication with NIST’s public mailing list. No deployed system was harmed. But the pace at which AI is now able to find cryptographic weaknesses suggests the entire timeline for post-quantum migration needs to accelerate.

For investors, this is a long-term story with short-term implications. The networks that move fastest to upgrade their cryptography — and that have governance structures capable of making hard decisions about vulnerable coins — will be better positioned to survive the coming decade. Those that drag their feet are betting that AI and quantum computing progress will be slower than every sign suggests it will be. That is not a bet anyone should want to lose.

Interestingly, Claude initially refused the AES problem, telling researchers it was “genuinely hard” and that there was “nothing easy to find.” After three short prompts, it produced a billion output tokens over three days and found the improvement. Verifying it took two Anthropic researchers nearly a month. The lesson: AI might not always get it right on the first try, but when it does find something, humans had better pay attention.

The cryptocurrency market remains highly volatile. This article is for informational purposes only and does not constitute financial advice.

Disclaimer: This article is for informational purposes only and does not constitute financial advice.