A public disagreement between Blockstream CEO Adam Back and Castle Island Ventures co-founder Nic Carter has reignited debate within the Bitcoin community over the urgency of quantum computing risks.
The dispute began after Carter publicly discussed Castle Island Ventures’ investment in Project Eleven, a startup focused on developing defenses against future quantum attacks on Bitcoin and other blockchain networks. Back responded critically on X, accusing Carter of overstating the danger and creating unnecessary alarm.
“You make uninformed noise and try to move the market or something. You’re not helping,” Back wrote, arguing that Bitcoin developers are already addressing potential quantum threats behind the scenes. According to Back, researchers and engineers prefer to work quietly on long-term solutions rather than turn speculative risks into public spectacle.
Carter strongly rejected that framing. He claimed that many Bitcoin developers are in “total denial” about how quantum computing could eventually compromise the cryptographic foundations that secure the network. Carter first disclosed Castle Island’s investment in Project Eleven in an October 20 Substack post, saying conversations with the startup’s CEO, Alex Pruden, fundamentally changed his view on the issue.
“I became extremely concerned about quantum threats to blockchains,” Carter wrote. “I put capital behind my convictions.”
The debate has drawn in other prominent voices from the crypto and investment world. Capriole Investments founder Charles Edwards recently warned that Bitcoin could face serious risk within two to nine years if quantum-resistant cryptography is not implemented in time. In contrast, investor Kevin O’Leary dismissed the idea of quantum computers being used to attack Bitcoin, arguing that such machines would be far more valuable in areas like medical research and artificial intelligence.
Back maintains that while making Bitcoin “quantum ready” is a sensible long-term goal, practical quantum threats are still decades away. He described the current state of the technology as “ridiculously early.”
Carter, however, points to growing government preparations for a post-quantum world and increasing investment in quantum computing firms as evidence that the risk should not be minimized.
At its core, the disagreement reflects a broader divide within the Bitcoin ecosystem: whether quantum computing represents an imminent existential threat or a distant challenge that can be addressed gradually. As of now, Bitcoin is trading around $87,000, but the debate over its long-term security is clearly far from settled.
