If a quantum computer capable of breaching current encryption emerged today, Bitcoin would likely come under siege — and remain unaware of it.
“Everything would appear to be legitimate access,” stated David Carvalho, CEO of the post-quantum infrastructure firm Naoris Protocol, in an interview with Cointelegraph. “When you think you’re observing a quantum computer, it has likely already had control for months.”
“You wouldn’t even realize,” he added.
IBM, Google, and government-supported labs are racing to bridge this gap, but time is running out. The US National Institute of Standards and Technology (NIST) has started approving post-quantum algorithms, yet most public blockchains still depend on encryption methods from the 1980s.
Currently, it remains a theoretical threat. But if it materializes, Bitcoin’s defenses could collapse quicker than the network could respond, Carvalho cautioned.
How a quantum attack could dismantle Bitcoin
Bitcoin’s foundational security relies on the Elliptic Curve Digital Signature Algorithm, or ECDSA, a cryptographic standard introduced in 1985. This system allows users to verify ownership with a private key, while only the corresponding public key is visible to the ledger.
Using Shor’s algorithm, a sufficiently robust quantum computer could hypothetically extract a private key from a public one. This would enable attackers to access wallets where the public key has previously been exposed onchain, including those from early Bitcoin (BTC) transactions.
“It would be impossible to demonstrate that a quantum computer was involved since it would appear as legitimate access,” said Carvalho. “You’d simply observe those coins spent as if their owners decided to spend them.”
Related: Bitcoin’s quantum countdown has already initiated, says Naoris CEO
Kapil Dhiman, CEO and founder of Quranium — a layer-1 blockchain startup dedicated to post-quantum security — warned that the most immediate and evident targets would be the oldest wallets.
“Satoshi’s coins would be vulnerable,” he mentioned to Cointelegraph. “If those coins are moved, trust in Bitcoin will shatter long before the entire system fails.”
In this situation, the blockchain would continue to process transactions normally. Blocks would be mined, and the ledger would remain unaltered, but ownership would have subtly shifted.
The current reality is that with more powerful GPUs and improved algorithms, brute-force attacks are becoming slightly more feasible. However, ECDSA with Bitcoin’s 256-bit keys remains far beyond the reach of classical computation.
Bitcoin lags behind traditional finance in post-quantum encryption
While banks, telecom networks, and government bodies are already trialing post-quantum encryption, most major blockchains still depend on 1980s technology.
“All blockchains have recognized this vulnerability as a fundamental issue,” Dhiman stated, referring to the potential that existing encryption methods like ECDSA could be compromised by quantum computing.
Shifting Bitcoin to a quantum-resistant framework would need a significant revamp of the network’s consensus rules, requiring broad cooperation among miners, developers, and users.
Related: Lost your Bitcoin in California? You might get it all back
Researchers have proposed initial pathways, including Bitcoin Improvement Proposal 360, which details possible routes for adopting new cryptographic methods, and the “Post Quantum Migration and Legacy Signatures Sunset” initiative, which phases out older signature methods. Ethereum developers are also exploring lattice-based signatures and other quantum-resistant solutions, though none have reached implementation.
In traditional finance, the transition is already in progress. The US NIST has approved several algorithms, and JPMorgan has trialed a quantum-safe blockchain in collaboration with Toshiba. SWIFT has begun providing post-quantum security training for its network.
“Traditional finance is actually ahead,” Carvalho said. “They have centralized control, budgets, and a single body that can implement upgrades. Crypto lacks that. Everything requires consensus.”
Some newer blockchain projects are positioning themselves as quantum-ready from inception. Naoris Protocol, led by Carvalho, was referenced in an independent proposal submitted to the US Securities and Exchange Commission discussing post-quantum standards, while Dhiman’s Quranium utilizes the NIST-approved Stateless Hash-Based Digital Signature Algorithm. Meanwhile, Quantum Resistant Ledger is a blockchain designed around XMSS hash-based signatures, a now-standardized NIST algorithm.
What if Bitcoin fails the quantum challenge?
For the average Bitcoin holder, the main worry is a sudden drop in confidence, potentially causing prices to fall and impacting traditional markets where institutional cryptocurrency adoption is increasing.
“There is a non-zero chance that it exists now. The consensus among scientific, research, and military institutions is to the contrary,” Carvalho stated.
“However, it would not be the first occasion that world-class cryptography had been compromised without public awareness,” he noted, referring to the Enigma cipher.
Used by Nazi Germany during World War II, the Enigma cipher was deemed unbreakable at that time. Yet cryptanalysts led by Alan Turing and his team at Bletchley Park discreetly deciphered it. The Allies kept this breakthrough under wraps to ensure Germany continued to use the cipher.
“When you think you’re observing a quantum computer, it has already been in control for months,” Carvalho alerted.
However, experts remain hopeful that quantum-secure blockchain systems can be developed and that the industry is working to align with standards that are already being implemented in traditional finance.
“Quantum-secure systems are attainable,” said Dhiman. “We need to start constructing them before the threat becomes tangible.”
For now, quantum threats are still hypothetical. Bitcoin’s encryption is robust, and computers capable of compromising it exist only in theory.
Magazine: Bitcoin vs. the quantum computer threat: Timeline and solutions (2025–2035)
