Citi has issued a warning about Bitcoin’s vulnerability to quantum computing, stating that the cryptocurrency faces an outsized threat compared to other digital assets. According to a research note from analyst Alex Saunders, dated May 18, the timeline for quantum machines to crack Bitcoin’s encryption is shrinking due to rapid technological advances. The report emphasizes that Bitcoin’s decentralized governance structure makes it particularly susceptible because protocol upgrades require extensive coordination among miners and node operators, a process that can take years.
The bank estimates that between 6.5 and 6.9 million Bitcoin, worth approximately $450 billion, have public keys already exposed on the blockchain. This includes wallets linked to the pseudonymous creator Satoshi Nakamoto. Such exposed keys could be vulnerable to a ‘harvest now, decrypt later’ strategy, where attackers collect encrypted data today for future quantum-enabled decryption. In contrast, proof-of-stake networks like Ethereum may be more agile in updating their protocols, though they present a larger attack surface overall.
Citi remains optimistic about the cryptocurrency’s long-term adaptability through post-quantum cryptography, but notes that proposed upgrades like BIP-360 and BIP-361 still require broad consensus. The broader Bitcoin ecosystem faces additional pressures from rising energy costs and the pivot of miners toward artificial intelligence, as highlighted by JPMorgan’s separate analysis on miner overvaluation. With Bitcoin trading near $76,900, the quantum threat adds another layer of strategic concern for investors.