Coinbase Advisory: Quantum Computing Could Expose Proof-of-Stake Blockchains to Attacks

Proof-of-stake blockchains could face greater exposure to future quantum computing attacks because the validator signatures used to secure those networks rely on cryptography that a powerful enough quantum computer could eventually break, according to a report released by cryptocurrency exchange Coinbase.

Released Tuesday by Coinbase's Independent Advisory Board on Quantum Computing and Blockchain, the report examines how advances in quantum computing could affect digital asset security. "The right time to prepare for a cryptographic transition is before it becomes urgent," a Coinbase Advisory Board spokesperson told Decrypt. "Our view is that customer assets are safe today, but the industry should not confuse 'not imminent' with 'not important.'"

Proof-of-stake networks like Ethereum and Solana rely on cryptographic signatures—BLS signatures for Ethereum validators and Ed25519 signatures for Solana validators and users—to help the network agree on blocks and maintain consensus. "Proof-of-stake chains have exposure in the signature schemes that validators use to secure the network," the advisory board said. "That means the challenge for proof-of-stake isn't just upgrading wallets; parts of the core consensus mechanism itself may need to be redesigned."

The report pointed to recent work by Ethereum developers, including a proposal by co-founder Vitalik Buterin in February to replace BLS validator signatures, KZG commitments, and ECDSA wallet signatures with quantum-resistant alternatives.

Launched in January, Coinbase's Independent Advisory Board on Quantum Computing and Blockchain brings together academic and industry experts to study how advances in quantum computing could affect blockchain security and to outline long-term solutions. The council includes researchers from Stanford University, the University of Texas at Austin, the Ethereum Foundation, Eigen Labs, Bar-Ilan University, and the University of California, Santa Barbara.

The council also identified digital signatures used by crypto wallets as another major long-term vulnerability. These signatures prove ownership of cryptocurrency and authorize transactions. If broken, attackers could impersonate wallet owners and move their funds. Wallets where public keys are visible on-chain are considered the most exposed. The report estimates that about 6.9 million Bitcoin fall into that category.

The report says current cryptocurrency systems remain secure because quantum computers capable of breaking modern cryptographic signatures do not yet exist. Machines capable of doing so would need to be far more powerful than today's quantum systems.

While much of the quantum threat discussion has focused on Bitcoin, the council said the network's core infrastructure—including its mining process, hash functions, and historical ledger—is not considered meaningfully vulnerable under current understanding. "A quantum computer running Grover's algorithm could, in theory, solve the proof-of-work challenge faster than a classical computer," the advisory board said. "However, at the scale of current proof-of-work puzzles, the overhead required to run Grover's algorithm on a quantum computer outweighs its theoretical advantage."

Experts warn that moving blockchains to quantum-resistant cryptography presents technical challenges due to quantum-safe signatures being significantly larger than current ones, which could affect transaction speed, storage, and costs. "The prudent thing to do is to prepare Bitcoin and give people the option to migrate their keys to a quantum-ready format," Blockstream CEO Adam Back told Bloomberg in a recent interview. "The longer time that Bitcoin users have in order to migrate their keys for custodians and exchanges to move their coins to a quantum-ready format, the safer it will be."

The report also raises the question of how networks should handle wallets that never upgrade. Lost keys, inactive accounts, and abandoned wallets mean some assets could remain exposed if quantum attacks become possible. "A cryptographically relevant quantum computer would still require a major leap from today's systems, but upgrading wallets, exchanges, custodians, and decentralized networks is a multi-year effort," the advisory board said. "That's why we wanted to publish now: to ground the conversation in science rather than hype, outline what is actually at risk, and help the industry start making practical migration decisions early."