Quantum computing is no longer a distant theoretical concern for the cryptocurrency industry. A new report from Citi warns that breakthroughs in quantum technology are arriving faster than expected, compressing the timeline for potential security risks to Bitcoin and other blockchain networks. The bank specifically highlighted Bitcoin as being particularly exposed due to its slower governance and upgrade process, which could delay the implementation of quantum-resistant cryptography.
Bitcoin, the largest cryptocurrency by market capitalization, relies on elliptic curve cryptography (ECC) for its digital signatures. This encryption method is widely considered secure against classical computers but could be broken by a sufficiently powerful quantum computer using algorithms like Shor's algorithm. If such a machine becomes operational, it could theoretically derive private keys from public keys, giving attackers the ability to spend funds from any wallet that has ever made a transaction (since the public key is revealed when a transaction is signed). This existential threat has been discussed for years, but the pace of quantum development has historically been slow enough to give the industry time to prepare.
According to Citi, that window is closing. The bank points to recent milestones in quantum computing, including advances in qubit stability, error correction, and the emergence of hybrid quantum-classical systems. These developments are being accelerated by artificial intelligence, which is helping researchers optimize quantum circuits and discover new materials for qubits. Security experts have warned that AI could reduce the time needed to build a cryptographically relevant quantum computer by years or even decades.
The implications go beyond cryptocurrency. The entire internet infrastructure that relies on public-key cryptography, including TLS/SSL, email encryption, and digital signatures, would be vulnerable. However, the financial stakes in crypto are particularly high because digital assets can be stolen instantly and irreversibly. Bitcoin alone has a market cap of over $1.2 trillion, making it a prime target for quantum attacks. Moreover, the transparency of blockchain transactions means that every past and future transaction that reveals a public key could become a vulnerability.
Citi notes that Ethereum and other proof-of-stake networks have a structural advantage in adapting to quantum threats. Ethereum's governance is more centralized through the Ethereum Foundation and its core developer community, which can push through upgrades like hard forks relatively quickly. In contrast, Bitcoin's upgrade process is deliberately slow and conservative, requiring broad consensus among miners, node operators, and the community. This cautious approach has served Bitcoin well in terms of security and stability, but it could become a liability if a quantum threat emerges suddenly.
Bitcoin's script system also poses challenges for implementing quantum-resistant signatures. The Bitcoin network uses the OP_PUSH_TX opcode and others that are tightly coupled to the current ECDSA (Elliptic Curve Digital Signature Algorithm). Switching to a quantum-resistant scheme like lattice-based cryptography would require a soft fork or a hard fork, and significant changes to the transaction format. While there have been proposals for quantum-safe Bitcoin upgrades, none have been formally adopted. The Bitcoin Improvement Proposal (BIP) process is slow, and there is no clear timeline for when the network might migrate.
Ethereum, on the other hand, has already begun exploring quantum-resistant features. The Ethereum Foundation has funded research into post-quantum cryptography, and the network's upcoming upgrades may include quantum-safe address formats. Additionally, Ethereum's account model allows for more flexible signature schemes than Bitcoin's UTXO model. Some layer-2 solutions on Ethereum are also experimenting with quantum-resistant technology, which could provide a fallback if the main chain is compromised.
Other cryptocurrencies are also taking steps to prepare. Projects like QRL (Quantum Resistant Ledger) have been built from the ground up using hash-based signatures that are resistant to quantum attacks. The IOTA Foundation has also announced a quantum-resistant version of its ledger. However, these smaller networks lack the liquidity and network effects of Bitcoin and Ethereum. The broader crypto industry is still in the early stages of adopting post-quantum cryptography, and many projects have not yet begun the transition.
The role of artificial intelligence in accelerating quantum computing cannot be overstated. Machine learning algorithms are being used to optimize quantum error correction codes, simulate quantum circuits, and even design new quantum gates. AI can also help identify vulnerabilities in existing cryptographic systems, potentially allowing attackers to exploit weaknesses before defenses are in place. Researchers have warned that the combination of AI and quantum computing could lead to a new class of cyberattacks that are both faster and more sophisticated than anything seen before.
Citi's report is part of a growing chorus of warnings from financial institutions and security experts. Earlier this year, the National Institute of Standards and Technology (NIST) finalized its first set of post-quantum cryptography standards, providing a roadmap for organizations to migrate. The U.S. government has also issued mandates for federal agencies to begin transitioning to quantum-resistant systems. However, the timeline for mass adoption remains uncertain. Estimates for the arrival of a cryptographically relevant quantum computer range from 10 to 30 years, but recent advancements suggest the lower end of that range may be more realistic.
For Bitcoin holders, the immediate risk is not that a quantum computer will appear tomorrow, but that the network's slow upgrade process could leave it vulnerable when a threat does emerge. The Bitcoin community must begin serious discussions about quantum resistance now, even if a fork is years away. Developers are exploring solutions like Taproot upgrades that could facilitate quantum-safe transactions, but these require broad adoption and testing. Some proposals suggest a soft fork to introduce new signature schemes, while others advocate for a hard fork that would change the fundamental cryptography of the network.
The broader crypto market is also at risk. Many altcoins use similar elliptic curve cryptography to Bitcoin, and even proof-of-stake networks that use BLS signatures could be vulnerable to quantum algorithms like Grover's algorithm, which can brute-force hash functions. However, proof-of-stake networks have the advantage of being able to rotate validators and update consensus mechanisms more easily. The biggest challenge for all blockchains is the sheer scale of the migration: every existing wallet, smart contract, and transaction history must be secured against future quantum attacks.
In addition to governance differences, the economic incentives for Bitcoin to upgrade are complex. The community values decentralization and immutability above all else, and any change to the core protocol is subject to intense scrutiny. A quantum-induced crisis might require a coordinated response that could involve freezing certain funds or rolling back transactions, which would go against Bitcoin's fundamental principles. Some argue that quantum resistance should be built into the protocol from the start, but others believe that the threat is still too remote to justify disrupting the network's stability.
The insurance industry is also paying attention. Lloyd's of London and other insurers have begun offering policies that cover losses from quantum attacks, but premiums are high and coverage is limited. For crypto exchanges and custodians, the threat of a quantum breach is becoming a material risk that must be disclosed to shareholders and regulators. The U.S. Securities and Exchange Commission (SEC) has asked companies to disclose their quantum readiness in financial filings, signaling that this is a governance issue as much as a technical one.
Meanwhile, the price of Bitcoin remains volatile, trading around $76,500 as of late May 2026. The quantum risk has not yet been fully priced into the market, but some analysts believe it could become a major factor in the coming years. If a credible quantum breakthrough is announced, the market could react sharply, with a flight to perceived safe havens like gold or even to quantum-resistant cryptocurrencies. The Federal Reserve and other central banks are also watching the situation, as quantum computing could undermine the cryptographic protections of digital currencies issued by central banks (CBDCs).
In conclusion, while the quantum threat to Bitcoin is not imminent, Citi's report underscores the urgency of preparing for a future where today's encryption is no longer secure. The crypto industry must invest in quantum-resistant technology and foster governance mechanisms that allow for rapid adaptation. Bitcoin's conservative approach has been a strength, but in the face of accelerating technological change, it could become a critical weakness.
Note: This article expands on the original report by including background on quantum computing risks, comparisons between Bitcoin and Ethereum governance, the role of AI in accelerating quantum development, and the broader implications for the crypto ecosystem.
Source: Coindesk News