18 May 2026 20:55 UTC - by Peace Longe
Citi warned Bitcoin faces outsized quantum risk due to slow governance, with roughly 6.5 to 6.9 million BTC already exposed on-chain.
➤ While post-quantum cryptography is a long-term solution, the pace of quantum advancements and the slow consensus for Bitcoin upgrades necessitate closer attention from investors.
➤ Approximately 6.5 to 6.9 million BTC are already exposed on-chain with vulnerable public keys, creating a 'harvest now, decrypt later' threat.
➤ Citi warns that Bitcoin faces a significant quantum computing risk due to its slow governance structure, making protocol upgrades difficult.
Citi warned Monday that Bitcoin faces an outsized quantum computing threat, with up to 6.9 million BTC already vulnerable.
Summary
• Citi’s May 18 digital asset research note says quantum computing advances are compressing the timeline for when machines could break Bitcoin’s encryption.
• Bitcoin is particularly exposed because its decentralised governance makes protocol upgrades slow and difficult to coordinate, unlike proof-of-stake networks.
• An estimated 6.5 to 6.9 million BTC have public keys already exposed on-chain, representing roughly one-third of circulating supply valued at around $450 billion.
Citi analyst Alex Saunders warned in a May 18 digital asset research note that accelerating quantum computing advances are shortening the timeline for risks to Bitcoin and broader internet infrastructure.
The bank said Bitcoin is particularly exposed because its conservative governance structure makes protocol upgrades slow and difficult to coordinate.
The Citi Institute has been tracking quantum risk to financial systems throughout 2026, estimating that a quantum-enabled attack on a major US bank could put $2 to $3.3 trillion of GDP at risk, as reported by The Quantum Insider in February.
“While large-scale quantum attacks remain a medium-term concern, the pace of progress has shortened the horizon and warrants closer attention from investors,” Saunders wrote in the note.
Bitcoin’s governance is its quantum weakness
Citi identified vulnerabilities tied to public keys already exposed on-chain. Older Bitcoin addresses using pay-to-public-key outputs left public keys permanently visible, including wallets believed to belong to Bitcoin’s pseudonymous creator Satoshi Nakamoto. The bank estimates 6.5 to 6.9 million BTC hold already-exposed keys, worth roughly $450 billion at current prices.
The report flagged a “harvest now, decrypt later” risk, where attackers collect encrypted data today for future quantum-enabled decryption. Proof-of-stake networks such as Ethereum may be better positioned to respond because they upgrade protocols more frequently, Citi said.
However, the bank warned they present a larger attack surface. The crypto.news Bitcoin price page shows Bitcoin currently trading at around $76,900.
How far away is the actual threat?
The bank said it remains constructive on crypto’s long-term ability to adapt through post-quantum cryptography. Proposed Bitcoin upgrades including BIP-360 and BIP-361 are in development but require broad consensus among miners and node operators, a process that historically takes years.
Broader Bitcoin ecosystem context matters here: as crypto.news reported in its Q1 2026 mining sector coverage, the Bitcoin network is navigating simultaneously rising energy costs, the AI pivot among miners, and now growing institutional scrutiny of its long-term cryptographic resilience.
JPMorgan has separately noted that miners pivoting to AI face high capital needs and potential shareholder dilution, underlining that the broader Bitcoin infrastructure is undergoing structural stress from multiple directions at once.
Categories rationale: The article's primary focus is on the threat posed by quantum computing to Bitcoin's cryptographic security, aligning with the 'quantum-computing' Level 1 category. Specifically, it delves into the 'cryptographic-security-risk' and 'long-term-institutional-concerns' within this domain.Characteristics justification: The article expresses significant concern and warning from Citi regarding Bitcoin's vulnerability to quantum computing, indicating a negative sentiment (-0.7). The topic of quantum risk to financial systems and the uncertainty surrounding the timeline and impact of these advancements contribute to a high uncertainty score (0.9). The novelty of this specific warning from a major financial institution suggests a higher entropy (0.85). The relevance is high (0.9) due to the specific warning from a reputable source about a critical infrastructure risk. Staleness is moderate (0.3) as quantum risk is an ongoing discussion, but this specific warning adds a new data point.Tag relevance: The selected tags (Citi, Bitcoin, quantum risk, encryption, governance, public keys, post-quantum cryptography, BIP-360, BIP-361, JPMorgan) are highly relevant as they represent the key entities, the core threat, the underlying technical vulnerabilities, the challenges in addressing the threat, and related institutional commentary discussed in the article.asset-types: others
rwa: false
entropy: 0.85
sentiment: -0.7
staleness: 0.3
relevance: 0.9
uncertainty: 0.9RWATimes slug: crypto-citi-warns-bitcoin-faces-quantum-risk-4118213146