Citi warned on Monday that Bitcoin faces a huge quantum computing threat, with up to 6.9 million Bitcoins already at risk.
summary
- A digital assets research note issued by Citi on May 18 says advances in quantum computing are compressing the timeline for when devices will be able to crack Bitcoin’s encryption.
- Bitcoin is particularly at risk because its decentralized governance makes protocol upgrades slow and difficult to coordinate, unlike proof-of-stake networks.
- An estimated 6.5 to 6.9 million bitcoins already have public keys exposed on-chain, representing roughly a third of the circulating supply worth about $450 billion.
Citi analyst Alex Saunders warned in a May 18 digital asset research note that accelerating progress in quantum computing is shortening the timeline for risks to Bitcoin and the broader internet infrastructure.
Bitcoin is particularly vulnerable because its conservative governance structure makes protocol upgrades slow and difficult to coordinate, the bank said.
The Citi Institute has been tracking quantum risks to financial systems throughout 2026, estimating that a quantum attack on a major US bank could put between $2 trillion and $3.3 trillion of GDP at risk. I mentioned By The Quantum Insider in February.
“Although large-scale quantum attacks remain a medium-term concern, the pace of progress narrows the horizon and warrants greater investor attention,” Saunders wrote in the note.
Bitcoin’s governance is its quantum weakness
Citi has identified vulnerabilities associated with public keys that have already been exposed on-chain. Old Bitcoin addresses that used public key payment outputs left public keys permanently visible, including wallets believed to belong to Bitcoin’s pseudonymous creator Satoshi Nakamoto. The bank estimates that between 6.5 and 6.9 million bitcoins contain exposed keys already, worth approximately $450 billion at current prices.
The report noted the risk of “harvest now, decrypt later,” where attackers collect encrypted data today for quantum decryption in the future. Proof-of-stake networks like Ethereum may be better positioned to respond because they frequently upgrade protocols, Citi said.
However, the bank warned that it represents a larger attack surface. Crypto news Bitcoin price page It shows that Bitcoin is currently trading at around $76,900.
How big is the actual threat?
The bank said it remains positive about cryptocurrencies’ long-term adaptability through post-quantum cryptography. Proposed Bitcoin upgrades including BIP-360 and BIP-361 are in development but require broad consensus between miners and node operators, a process that historically takes years.
The broader context of the Bitcoin ecosystem is important here: such as crypto.news I mentioned In its coverage of the mining sector for the first quarter of 2026, the Bitcoin network navigates at the same time as rising energy costs, a pivot to artificial intelligence among miners, and now increasing institutional scrutiny of the crypto’s long-term resilience.
JP Morgan separately male That miners turning to AI face high capital needs and potential shareholder dilution underscores that the broader Bitcoin infrastructure is subject to structural pressures from multiple directions simultaneously.
