A recent research note from Citi analysts has raised concerns about quantum risks that may alarm institutional bitcoin investors, as explained by Tabar.
By Samir Tabar|Edited by Betsy Farber Jun 10, 2026, 4:07 p.m. 4 min readMake preferred on (Andriy Onufriyenko/Getty Images)If Bitcoin and Ethereum had launched simultaneously, Bitcoin likely would have remained unnoticed. I liquidated all Bitcoin held by Bit Digital and redirected the funds into Ethereum. I have established one of the largest corporate Ethereum treasury holdings globally and have publicly stated that we will never sell it. When asked to provide the strongest rationale for this belief, I pointed to March 30, 2026, when Citi corroborated my views.
In a note published on May 18, Citi analysts cautioned that advancements in quantum computing have accelerated the timeline for potential attacks on digital assets. They concluded that Bitcoin is at a significantly higher quantum risk compared to Ethereum, a difference rooted not only in technology but also in governance.
This conclusion aligns with a significant study released in late March by Google Quantum AI in partnership with Stanford University and the Ethereum Foundation, which determined that the computational power needed to breach Bitcoin's cryptographic security is approximately 20 times less than previously thought. A sufficiently powerful quantum computer with under 500,000 physical qubits could potentially derive a Bitcoin private key from its public key in about nine minutes. While such a machine does not exist currently, the opportunity for responsible action is diminishing faster than many institutions recognize. When both Google and Citi raise alarms in the same quarter, this concern is no longer marginal. It is the critical issue, and it directly implicates Bitcoin.
The Vulnerability of Bitcoin
Bitcoin's security is based on elliptic curve digital signature algorithms. When a transaction is made, the public key is momentarily exposed on the blockchain. In classical computing, reversing this to obtain the private key is impractical. However, quantum computers utilizing Shor's algorithm could theoretically achieve this during the brief period a transaction is broadcast. The Google study not only confirms this theory but quantifies it with a clarity that eliminates any comforting ambiguity.
Nic Carter, co-founder of Coin Metrics and a prominent figure in digital assets, has been sounding this alarm for months. In a series of articles starting in October 2025, Carter labeled quantum computing as "the biggest long-term risk to Bitcoin's core cryptography" and criticized developers for "sleepwalking towards collapse." He estimates that a quantum computer could feasibly undermine elliptic curve cryptography as soon as 2028. Approximately 6.9 million BTC could be at risk at a sufficient quantum level, including legacy wallets and Taproot outputs, which already accounted for over 21% of Bitcoin transactions in 2025.
Bitcoin's Governance Challenges
One might wonder if Bitcoin could simply upgrade to mitigate this risk. Theoretically, yes. However, the reality is that this is where the risk amplifies.
Bitcoin's governance is purposefully conservative and consensus-driven, resulting in a notably slow process. The SegWit upgrade took around 8.5 years from conception to widespread implementation, while Taproot took about 7.5 years. The current proposals addressing quantum risks, BIP-360 and BIP-361, remain in the draft or early testnet phase as of 2026. Transitioning the entire base layer to post-quantum signatures would represent the most contentious change Bitcoin has ever attempted. As Carter noted, most Bitcoin Core developers have shown limited urgency regarding this issue, creating a significant governance risk for any institution holding Bitcoin in its treasury. Quantum advancements will not wait for committee consensus.
Ethereum's Proactive Measures
In contrast, Ethereum's strategy for quantum resistance is not a frantic response. It is a well-structured roadmap that is already underway, based on the NIST post-quantum cryptography standards finalized in August 2024.
The Pectra upgrade, which launched on Ethereum mainnet in May 2025, introduced EIP-7702, serving as a crucial step toward complete account abstraction. Unlike Bitcoin, which necessitates a network-wide hard fork, Ethereum's design allows individual accounts to select their own signature verification and transition to quantum-safe signatures voluntarily. The forthcoming Hegotá hard fork, planned for the latter half of 2026, will further integrate this at the protocol level. The Ethereum Foundation has established clear milestones aiming for the completion of core post-quantum infrastructure by around 2029, with active interoperability development networks already functioning across various clients.
The contrast with Bitcoin's governance stagnation is glaring. Ethereum was engineered, unlike Bitcoin, to facilitate such foundational upgrades. This is by design.
Implications for Institutions
For corporate treasurers and sovereign wealth managers, quantum risk is no longer just a hypothetical scenario to be ignored. Governments are already treating it as a pressing operational issue. U.S. federal agencies faced a deadline in April 2026 to present post-quantum cryptography transition plans under National Security Memorandum 10. The EU has set a target for critical infrastructure to achieve quantum resistance by 2030. The G7 Cyber Expert Group released a coordinated financial sector roadmap in January 2026. This compliance framework will gradually extend to digital asset treasury holdings.
Institutions holding Bitcoin must consider whether they are willing to manage an asset that lacks a clear quantum-resistance roadmap, progresses at a glacial pace, and has a developer community divided on the urgency of the matter.
Conversely, institutions contemplating Ethereum must evaluate whether they prefer an asset with a defined, transparent, and actively pursued upgrade path.
Ethereum emerges as the more adaptable, capable, and resilient asset. I have committed the balance sheet of a Nasdaq-listed company to support this belief. The Google paper provides a definitive, technically grounded answer to the pressing question in digital asset treasury management: which asset is designed to endure?
While Ethereum is not without flaws, no asset is perfect. However, in the context of quantum risk, it stands out as the asset engineered to withstand the challenges ahead. If Carter and Google are correct, this distinction will become increasingly significant, and sooner than many anticipate.
quantum computingNote: The opinions expressed in this piece belong to the author and do not necessarily represent those of CoinDesk, Inc. or its affiliates.
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