JAN3 CEO Samson Mow has challenged calls to accelerate Bitcoin’s transition to post-quantum cryptography, warning that unproven defenses could introduce immediate security and scalability problems.

The debate followed Anthropic’s announcement that its Claude AI system had identified weaknesses in two cryptographic designs. 

According to the company, Claude Mythos Preview found a previously unknown attack against HAWK, a digital-signature scheme intended to resist quantum computers, after 60 hours of analysis. 

Anthropic said the finding reduced the scheme’s key strength by half following two years of expert review.

Anthropic also reported that Claude found a way to accelerate an attack against a reduced version of the Advanced Encryption Standard by between 200 and 800 times. 

The result concerned a research variant rather than the complete AES cipher used in deployed systems.

The findings added urgency to an existing discussion about whether the digital asset industry should begin preparing for quantum attacks. 

Philip Martin cited recent quantum-computing research from Google and the California Institute of Technology as a signal that work should begin despite uncertainty over the timeline.

On April 1st, 2026, Coinbase CEO Brian Armstrong shared Martin’s post and wrote, “going to start spending time on this personally - seems like we all need to solve it sooner rather than later.”

Mow argued that adopting post-quantum signatures before the alternatives have undergone extensive scrutiny could expose Bitcoin to attacks using conventional computers.

“Hastily changing from ECDSA/Schnorr to PQ signatures may make Bitcoin vulnerable to classical computing attacks today. Simply put: make Bitcoin safe against quantum computers just to get pwned by normal computers,” he wrote.

Mow said research should continue but maintained that Bitcoin should not activate a network-wide replacement for its current signature systems until quantum computers present a clear threat. 

He praised work by Blockstream and cryptographer Jonas Nick on the hash-based signature schemes SHRINCS and SHRIMPS. 

Mow argued that these schemes have a smaller mathematical attack surface than lattice-based alternatives such as HAWK. 

SHRINCS has been deployed through the Simplicity programming language on Blockstream’s Liquid sidechain.

Transaction capacity is another concern. Citing Bitcoin developer Jonas Schnelli, Mow said some proposed post-quantum signatures could be between 10 and 125 times larger than those currently used. 

Larger signatures would consume more block space and could reduce transaction throughput, potentially reopening disagreements reminiscent of the Blocksize Wars.

Mow also warned that post-quantum proposals could be used to introduce backdoors through random-number generators or encryption schemes.

The dispute revived earlier disagreements between Mow and Armstrong dating to the Blocksize Wars. 

In Mow’s view, Armstrong was again supporting a course of action and timeline before the technical tradeoffs had been fully evaluated.

On timing, he estimated that quantum computers capable of threatening Bitcoin remain 10 to 20 years away, while acknowledging that preparatory research is already underway. 

Forecasts for cryptographically relevant quantum computers remain uncertain.

He further explained that address reuse in Coinbase’s wallet infrastructure, including Coinbase Prime, could leave funds more exposed to a future quantum attack. 

Spending from certain types of Bitcoin addresses reveals their public keys, which a sufficiently capable quantum computer could theoretically use to calculate the corresponding private keys. 

The disagreement is therefore primarily about timing rather than whether Bitcoin should prepare. 

Armstrong’s position emphasizes the long lead time required to protect a global network, while Mow argues that deploying immature cryptography could create serious risks before quantum computers become a practical threat.