Quantum computing has not yet become an immediate threat to crypto assets, but preparing for a possible future attack could take years. An estimated $2 trillion in digital assets rely on elliptic-curve cryptography, compared with a total crypto market value of about $2.8 trillion. Reducing that exposure will require coordinated changes by blockchain networks, custodians and asset holders. There is no common mandate for migration, leaving open who will pay for upgrades and what should happen to assets whose owners cannot be reached.
Post-quantum standards are ready; networks still need upgrades
Elliptic-curve cryptography is widely considered vulnerable to a sufficiently powerful quantum computer. In 2024, the US National Institute of Standards and Technology (NIST) approved post-quantum cryptography standards, giving systems alternatives to adopt. But the standards do not make existing crypto assets quantum-resistant on their own: blockchains must first support new signature types before wallets and custody providers can adapt.
For Bitcoin, the concern centers on the cryptography used for signatures. It does not mean the network’s hashing, mining or historical ledger would all fail at once. Even if the exposure is concentrated at the wallet level, the financial consequences could spread beyond individual holders. Losses involving large asset balances or stablecoin controls secured by vulnerable keys could affect counterparties, markets and other protocols.
Larger signatures bring bandwidth and storage costs
Migration also poses practical engineering challenges. A conventional ECDSA signature is about 64 bytes, compared with roughly 3,309 bytes for an ML-DSA-65 signature—about 52 times larger. An ML-DSA-87 signature is about 4,627 bytes, before accounting for the larger public keys that also come with the scheme.
Bigger signatures increase network traffic and storage needs. They could also affect fees, throughput assumptions, and hardware wallets and custody systems designed around older data sizes. Multisignature arrangements can reduce some operational risks, but adding more locks will not resolve a cryptographic weakness if the signatures still rely on the same vulnerable mechanism. Cold storage can limit the risk of stolen keys or compromised devices, but it does not prevent an attacker from deriving a private key from a public key if the underlying cryptography is broken.
Responsibility for migration is spread across the ecosystem. Protocol developers need to add support; custodians depend on the underlying networks to provide it; and users holding assets in self-custody must take action themselves. Node communications, consensus, zero-knowledge proofs, cross-chain bridges and custody infrastructure each rely on their own cryptographic assumptions. Replacing transaction signatures alone would not address every part of the system.
Early movers face costs; lost assets pose a separate problem
While the risk remains distant, participants may have an incentive to wait. Organizations that upgrade early must fund development, modify custody systems and update hardware and procedures. Those that move later can watch how the technology and standards mature. Individually cautious decisions could stretch the industry-wide transition over a longer period.
Large exchanges and custodians, which control substantial amounts of assets, may move first. Smaller providers and individual holders could take longer. Coinbase has also highlighted the challenge posed by abandoned or inaccessible wallets: voluntary migration cannot ensure dormant accounts are updated, and holders who have lost their keys cannot complete the process.
If old addresses remain usable indefinitely, unmigrated assets could stay exposed. A migration deadline, by contrast, would force decisions about assets that have not moved, including whether to freeze or destroy them or impose other restrictions. Each option could prompt governance disputes, and there is no straightforward answer at present.
Deadline rules will shape how unmigrated assets are handled
Possible approaches include phasing out older signatures, having exchanges and custodians restrict vulnerable address types, or encouraging migration through insurance terms, institutional counterparties and regulatory requirements. No common rules or timetable have been established. An open-ended transition would avoid immediate pressure to dispose of assets, but could leave old keys in the system for years. A firm deadline would bring the question of what to do with unmigrated assets forward.
Google’s proposed 2029 migration target applies to its own systems. It does not mean quantum computing capabilities will arrive that year, nor does it set a security deadline for the crypto industry. Still, upgrades spanning protocols, wallets, custodians, exchanges and individual holders take time. The market’s challenge is not only to judge when quantum computers might threaten existing cryptography, but also to agree on migration requirements and rules for assets that cannot be moved before that point.