Post-quantum cryptography could make Bitcoin’s signature sizes balloon by as much as 125 times — a technical reality now fueling a sharp debate over how fast the network should act.
Mow Calls Out The Rush
Samson Mow, founder of Bitcoin firm Jan3, went public over the weekend with a pointed warning: moving too fast on quantum security could leave Bitcoin more exposed, not less.
His comments came after Coinbase CEO Brian Armstrong and the company’s chief security officer, Philip Martin, called on the industry to start acting now against quantum computing threats.
Mow pushed back hard. A rushed transition to post-quantum cryptography, he said, risks opening up fresh vulnerabilities — including compatibility breakdowns and a sharp drop in how many transactions the network can handle at once.
“Simply put: make Bitcoin safe against quantum computers just to get pwned by normal computers,” Mow wrote on X.
It’s been almost 10 years since the Blocksize Wars ended and Brian hasn’t changed at all.
He still carries the exact same complete lack of humility and understanding. Brian forms the opinion first, along with a prescribed course of action and timeframe, instead of starting by… https://t.co/Ti7QV63e7P
— Samson Mow (@Excellion) April 4, 2026
A Ghost From Bitcoin’s Past
At the center of his concern is block size — the cap on how much transaction data fits inside a single Bitcoin block. Larger post-quantum signatures mean more data per transaction, which means fewer transactions per block, which means a slower and more congested network.
Former Bitcoin developer Jonas Schnelli put numbers to it, and Mow cited them directly. The implications go beyond speed. Block size has been a flashpoint before.
Between 2015 and 2017, a bitter community dispute over whether to expand Bitcoin’s block size tore the ecosystem apart and ultimately led to a chain split.
That fight raised deep questions about decentralization, network security, and who really gets to decide Bitcoin’s direction. Mow is warning the same battle could be coming back — what he’s calling “Blocksize Wars 2.0.”
Where Mow Draws The Line
Mow isn’t saying quantum threats should be ignored. His argument is about timing, not priority. Research on potential solutions is already underway, he said, and that work should continue.
But quantum computers capable of cracking Bitcoin’s encryption, he argued, are still a decade or two away at minimum. Rushing a fix for a threat that doesn’t yet exist, he said, creates real risks today in exchange for protection against something hypothetical tomorrow.
The debate is gaining urgency as new research from Google and the California Institute of Technology has stoked fresh concern about how quickly quantum computing may develop.
Armstrong and Martin flagged those findings as reason enough to move the timeline up. Mow’s position: the cure could be worse than the disease, at least for now.
Featured image from Trade Brains, chart from TradingView
