Quantus: Quantum Computers Could Break $2T in Crypto by 2030

Quantus released a report saying advancing quantum computers could break the signature systems that secure more than $2 trillion in cryptocurrency and that Bitcoin and Ethereum face urgent migration challenges because public keys remain permanently on-chain.

The report explains the technical risk centers on Shor’s algorithm. A sufficiently powerful quantum computer could factor large numbers and solve discrete logarithms, undermining RSA and elliptic-curve schemes such as ECDSA and Ed25519 that secure many blockchains.

Quantus points to recent progress in quantum hardware and cryptanalytic research, including improvements in error correction, gate fidelity and resource estimates, and says those changes move a plausible threat window toward 2030. The National Institute of Standards and Technology finalized its first post-quantum cryptography standards in August 2024; Quantus says the crypto industry has not yet agreed on a coordinated adoption path.

Blockchains face a harder migration than many internet services because public keys and signatures remain visible on-chain once they appear. Moving value to quantum-resistant addresses would require coordinated action by wallet providers, exchanges, custodians, validators and governance bodies.

The report estimates that more than $2 trillion in digital assets are secured by signature schemes vulnerable to a large quantum computer. It also cites estimates that between 2.3 million and 3.7 million bitcoins are permanently lost because owners no longer control the private keys, so those outputs cannot be migrated and remain exposed on-chain.

Quantus compared signature sizes to illustrate technical costs. A typical Bitcoin ECDSA signature and public key consume about 97 bytes of payload. A transaction using ML-DSA-87, a candidate post-quantum signature, carries roughly 7,187 bytes. That represents about a 70-fold increase in signature payload and would increase pressure on block space and throughput without architectural changes or new scaling approaches.

BIP 360 has been proposed as a possible Bitcoin migration route, but Quantus says it does not resolve all issues, including support in hardware wallets and what to do with coins that cannot be migrated.

The report warns the vulnerability extends beyond individual wallets. Stablecoin administrator keys, bridge validators, oracle networks, multisignature custody systems and governance contracts also rely on classical signatures. A cryptanalytic break at those points could affect lending markets, derivatives, automated market makers and institutional custody arrangements.

The report includes a warning from Quantus CEO Christopher Smith: “Crypto does not get a clean warning bell before Q‑Day. If the industry waits until the threat is obvious, users will be asked to move value under pressure.” Auryn Macmillan, co-founder of Gnosis Guild, recommended a firm timetable: “The only practical solution is to set a hard deadline for account owners to migrate their tokens to quantum-safe accounts, after which all tokens held in vulnerable accounts will be permanently frozen.”

The document notes some internet firms have started adopting post-quantum algorithms and that Quantus is developing a quantum-secure Layer 1 blockchain. The report frames the central question as whether the crypto ecosystem can organize a mass migration before quantum hardware reaches the scale needed to threaten current signature schemes.