Post-quantum cryptography could increase Bitcoin’s signature size by up to 125 times. This is now a technological reality that is giving rise to a sharp debate about how fast networks should operate.
Mow shouts rush
Samson Mow, founder of Bitcoin company Jan3, issued a sharp warning when he went public last weekend: This means that advancing quantum security too quickly could leave Bitcoin more exposed.
His comments come after Coinbase CEO Brian Armstrong and the company’s Chief Security Officer Philip Martin urged the industry to take action now to combat the threat of quantum computing.
Mo Wu pushed back hard. He said a hasty transition to post-quantum encryption risks introducing new vulnerabilities, including compatibility issues and a sharp decline in the number of transactions the network can handle at once.
“Simply put, make Bitcoin safe from quantum computers so it cannot be attacked by regular computers,” Mow wrote on X.
Almost 10 years have passed since the end of the block size war, but Brian hasn’t changed at all.
He still completely lacks humility and understanding. Instead of starting, Brian first forms an opinion with a predetermined course of action and time frame… https://t.co/Ti7QV63e7P
— Samson Mou (@Excellion) April 4, 2026
Ghosts from Bitcoin’s past
At the center of his concern is block size, or the limit on how much transaction data can fit into a single Bitcoin block. Larger post-quantum signatures mean more data per transaction, which means fewer transactions per block and a slower and more congested network.
Former Bitcoin developer Jonas Schnelli put the numbers to this, and Mow quoted them directly. That means more than speed. Block size has been a flashpoint before.
BTCUSD trading at $68,731 on the 24-hour chart: TradingView
Between 2015 and 2017, a fierce debate broke out in the community over whether to expand Bitcoin’s block size, fragmenting the ecosystem and ultimately leading to a chain split.
The fight has raised deep questions about decentralization, network security, and who will actually decide the direction of Bitcoin. Mow is warning that the same battle could happen again, in what he calls “Blocksize Wars 2.0.”
Image: Wccftech
Where Mow draws the line
Mow is not saying quantum threats should be ignored. His argument is about timing, not priorities. He said research into potential solutions was already underway and that work should continue.
However, he argued that a quantum computer capable of cracking Bitcoin’s encryption is still at least 10 to 20 years away. Rushing to fix for threats that don’t yet exist creates real risks today at the expense of protecting against hypothetical threats tomorrow, he said.
The debate is gaining urgency as new research from Google and the California Institute of Technology raises new concerns about how quickly quantum computing can advance.
Armstrong and Martin flagged these discoveries as reason enough to move the timeline forward. Mow’s position: The cure may be worse than the disease, at least for now.
Featured image by Trade Brains, chart by TradingView
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