Bitcoin’s post-quantum cryptography upgrade clash: Mow warns on timing, blocksize risks
Bitcoin’s post-quantum cryptography upgrade debate is intensifying as stakeholders look toward a 2029 migration deadline. JAN3 founder Samson Mow criticized Coinbase’s Brian Armstrong for pushing a “sooner” post-quantum cryptography switch, arguing that untested changes could expose BTC to attacks from today’s classical computers.
Mow’s core technical concern is that post-quantum cryptography signatures may be far larger (estimated 10–125x). Bigger signatures could require larger blocks, reduce transactions per block, and potentially reduce throughput—raising fears of a “blocksize wars 2.0” scenario. He also cited claims that adopting current PQ approaches could heavily slow Solana (around a 90% slowdown), framing the broader scalability impact beyond Bitcoin.
The dispute is gaining momentum after a Google Quantum AI report suggesting crypto security may erode sooner than previously thought. Google estimates quantum processors might need ~500,000 physical qubits or 1,200–1,450 stable logical qubits to compromise security, and warned that as many as ~7 million BTC tied to vulnerable keys could be at risk on a shorter timeline.
Not everyone is alarmed. Grayscale’s Zach Pandl said quantum computers are not an immediate threat to public blockchains, but preparation should accelerate. Meanwhile, Charles Edwards argued BTC may struggle to reach a new all-time high without PQ migration, while Adam Back suggested scalable, physical quantum hardware may still be years away.
For traders, this news is less about an imminent hack and more about how governance and protocol changes under timing pressure could affect BTC’s long-run security posture and network performance expectations.
Neutral
The combined articles frame the issue as a governance-and-protocol-timing risk rather than an immediate break of Bitcoin security. Mow’s warnings highlight potential scalability and compatibility downsides if Bitcoin adopts post-quantum cryptography too quickly, while Google’s report increases the urgency by suggesting progress could make vulnerable keys risky on a shorter timeline. However, multiple commentators (e.g., Grayscale) argue there is no direct, near-term threat, which limits the chance of a sharp, one-direction price move. Net effect: sentiment may sway with headlines about “blocksize wars 2.0” and migration urgency, but the lack of an immediate exploit makes the price impact on BTC more likely to be modest and range-bound—hence neutral.