As quantum computing advances, a recurring question surfaces: could quantum computers eventually compromise Bitcoin or Ethereum? The short answer is it isn’t an imminent concern. However, corporations holding digital assets long-term have a compelling reason to proactively manage this risk today.

Why Quantum Computers Pose a Threat to Cryptocurrencies

Bitcoin and Ethereum ownership rests entirely on cryptography. Users prove ownership by signing transactions with a private key using elliptic curve cryptography. With today’s classical computers, deriving a private key from a public key is computationally infeasible.

The risk emerges if a sufficiently powerful, fault-tolerant quantum computer is built. Shor’s algorithm can factor large numbers and solve discrete logarithm problems exponentially faster than classical computers, theoretically undermining digital asset cryptography. A quantum computer large enough to run Shor’s algorithm could fundamentally threaten current elliptic curve cryptosystems.

Source: Google Research, “Safeguarding cryptocurrency by disclosing quantum vulnerabilities responsibly”  (2026.03.31)

“This is an approximately 20-fold reduction in the number of physical qubits required to solve ECDLP-256.”

In March 2026, Google Quantum AI demonstrated that breaking the Bitcoin and Ethereum elliptic curve cryptosystem (secp256k1) requires roughly 20 times fewer physical qubits than previously estimated, drawing considerable industry attention.

No quantum computer capable of such an attack exists today. For institutions holding digital assets long-term, the approach isn’t to panic about imminent danger, but to manage the cryptographic transition as a structural risk over the coming decades.

The Irreversible Risk of Exposed Public Keys

Source: Simple Mining, Can Quantum Computing Break Bitcoin? A Technical Reality Check (2026.01.28)

Quantifying the Risk: Approximately 28.6% of the circulating Bitcoin supply (6 million BTC) currently has exposed public keys. This includes the famous “Satoshi coins” (P2PK) and addresses that have been reused, making them vulnerable to future quantum decryption (“Harvest Now, Decrypt Later”) without needing to break SHA-256 hashing.

Blockchain transactions are permanent and public. Bitcoin wallets can expose their public keys depending on the address type, and any Ethereum account that has sent a transaction has a permanently visible public key. According to official Ethereum documentation, a powerful quantum computer could eventually derive a private key from an exposed on-chain public key.

Information once made public cannot be undone. Obtaining a private key grants full authority to move the associated assets. An attacker recovering a private key can transact exactly as the legitimate owner would.

Industry estimates indicate roughly 6.04 million Bitcoin have exposed public keys due to past transactions, accounting for 28.6% of the 21 million supply cap. Of this, structural exposure from early Satoshi-era coins (P2PK) and reused addresses accounts for 1.92 million BTC (9.6%). This data underscores how crucial wallet management and custody practices are in minimizing public key exposure.

Source:  Ethereum – Post-quantum cryptography on Ethereum (2026. 07. 12)

“The Ethereum Foundation has a dedicated post-quantum research team, and a structured “Lean Ethereum” roadmap targeting 2029 for full post-quantum protection”

Consequently, Post-Quantum Cryptography (PQC) standardization is well underway. The Ethereum Foundation launched a dedicated post-quantum research team this past January and published its “Lean Ethereum” roadmap, targeting full post-quantum protection by 2029.

Who Actually Manages the Migration?

A new post-quantum cryptographic standard does not automatically secure existing wallet assets. Wallets with exposed public keys will likely require migrating assets to new quantum-resistant addresses or accounts.

The critical question is who executes this migration and when. In a corporate setting, this becomes considerably more complex. Staff turnover, restructuring, and multi-step approval protocols can severely complicate asset transfers. Tracking which wallets have migrated to a new cryptographic standard constitutes a significant operational risk.

Securing digital assets isn’t merely about keeping a private key safe. It requires a resilient organizational structure capable of continuously responding to an evolving security landscape.

The Role of Professional Custody

Source: Glassnode research – Measuring Bitcoin’s Quantum-Exposed Supply (2026. 05. 20) – Bitcoin Supply by Quantum Safety (Share)

“Structural exposure accounts for 1.92M BTC, equivalent to 9.6% of issued supply. … underscoring the role of wallet hygiene and custody practices in reducing public-key exposure.”

For corporations managing large digital asset volumes long-term, the key question is whether they possess the internal processes to independently monitor and address migration issues. This is where an institutional-grade partner delivers value. Beyond simple storage, they maintain operational systems to continuously track and respond to network upgrades, security vulnerabilities, and cryptographic transitions.

Through its flagship Prime Custody Solution, BDACS provides institutional-grade digital asset management built on Multi-Party Computation (MPC) infrastructure and a robust Anti-Money Laundering (AML) framework. Utilizing an MPC-CMP architecture developed with a global infrastructure partner, BDACS never generates or stores a complete private key in a single location. Cryptographic information is distributed across multiple independent environments to jointly sign transactions. This fundamentally mitigates the Single Point of Failure (SPOF) risk, where a single compromised device or administrator could lead to total asset loss.

While utilizing professional custody doesn’t automatically erase quantum risks, transitioning to quantum resistance requires upgrades at both the protocol and wallet infrastructure levels. The practical advantage of professional custody lies in leveraging dedicated infrastructure and operational expertise rather than tracking complex technological shifts independently.

Self-Custody’s Limit: It Doesn’t End at “Is It Safe Today?”

Purchasing a hardware wallet and locking a mnemonic phrase in a safe doesn’t guarantee asset security for the next 20 years. Blockchain technology continuously evolves. Cryptographic standards change, wallet infrastructure adapts, and new attack vectors emerge. Quantum computing stands as one of the most significant variables in that long-term evolution.

For individuals, self-custody remains a viable option. However, for companies managing massive corporate balance sheets in digital assets, relying on professional custody services equipped with dedicated security infrastructure, operational systems, and ongoing technical response capabilities is a far more rational choice than holding private keys directly.

Ultimately, digital asset custody isn’t simply about holding a key on a client’s behalf. It’s about keeping assets continuously secure amidst evolving technologies and threats. This is exactly why the role of professional digital asset custody will grow increasingly critical as the quantum computing era approaches.

FAQ

Q: Could a quantum computer break Bitcoin or Ethereum right now?

No. A fault-tolerant quantum computer capable of running Shor’s algorithm at the scale needed to break elliptic curve cryptography doesn’t exist today. However, as resource estimates have dropped several times in 2026 alone, it is increasingly urgent for companies holding long-term assets to prepare for future shifts.

Q: What is the difference between self-custody and professional custody?

Self-custody means individuals directly manage their own private keys. Professional custody encompasses secure key storage, continuous monitoring, and active response systems for network upgrades, cryptographic transitions, and emerging security threats, operating entirely like a regulated financial institution.

Q: When should companies start preparing for a post-quantum transition?

While the threat isn’t imminent, organizations holding wallets with previously exposed public keys are strongly advised to track standardization developments and understand migration procedures in advance.