1200 Qubits Estimated, Pressure on Bitcoin and Ethereum Transition

Warnings that quantum computers could threaten the existing signature systems of Bitcoin (BTC) and Ethereum (ETH) have resurfaced as a key issue in cryptocurrency security. The core concern is not that the networks will collapse immediately, but that assets and protocols with exposed public keys must prepare for a transition to encryption in advance.

Google Quantum AI published a paper on March 31, estimating the resources needed to break the secp256k1-based 256-bit elliptic curve cryptography used by BTC and ETH. Co-authors Ryan Babbush, Hartmut Neven, and Dan Boneh proposed combinations of fewer than 1200 logical qubits and fewer than 90 million topological gates, or fewer than 1450 logical qubits and fewer than 70 million topological gates.

The paper explains that if superconducting architecture, a physical error rate of 10 to the power of minus 3, and planar connectivity are assumed, circuit execution could be possible in minutes, and the required physical qubits could be less than 500,000. On the same day, Google stated on its official blog that the cryptocurrency industry should prepare for proactive transitions rather than reactive responses.

This estimate does not imply that quantum computers have already reached a level capable of launching attacks. However, as Google outlined a goal for post-quantum cryptography transition by 2029 on its official blog, there is a trend where the transition timelines of big tech and standard organizations are beginning to influence cryptocurrency wallets and custodial infrastructures.

The attack scenario involves an "on-spend" attack, where the public key is reverse-engineered during a transaction. BTC has a window of time between when a new transaction is added to the memory pool and when it is included in a block. Although ETH has shorter block times, the structure where the public key of already transacted accounts remains on-chain poses a separate risk.

Public key cryptography involves using separate public and private keys. Users sign transactions with their private keys, while the network verifies the validity of the signatures based on the public keys. If a sufficiently powerful quantum computer can reverse-engineer the private key from the public key, the security premise of the existing signature system could be undermined.

Ethereum's official documentation states that quantum computers pose a long-term threat to ECDSA, BLS signatures, KZG commitments, and zero-knowledge proof systems. However, it clarified that the current threat is not an "imminent threat." Ethereum has set 2029 as the target date for transitioning to quantum resistance in its Lean Ethereum roadmap.

The issue for Bitcoin is more about consensus than technology. CoinDesk reported that approximately 6.9 million BTC are in structures with exposed public keys. This is not an immediately stealable amount but an estimate based on the types of addresses and transaction histories where public keys are revealed on-chain.

Research proposals addressing quantum-resistant wallet support and consensus transitions have been submitted to the Bitcoin Core repository, but this issue is currently in a "no plans to proceed" state. Previous discussions have ultimately led to the need for protocol changes, wallet compatibility, and reflections from exchanges and custodians.

Ethereum is also not at an automatic resolution stage. CoinDesk reported that the top 1000 Ethereum wallets hold approximately 20.5 million ETH, and at least 70 major admin keys are exposed on-chain. Existing smart contracts, bridges, and layer 2 solutions each require key replacements and code modifications.

The developer community is discussing ways to combine post-quantum signatures with STARK aggregation. Proposals such as "EIP-8288: Frame Type for PQ Signatures and STARK Aggregation" have been raised in Ethereum Magicians. Account abstraction, keystore formats, and layer 2 compatibility are identified as challenges that need to be addressed during the transition process.

Industry reactions are mixed. Some communities advocate for the urgent relocation of assets with exposed public keys, while others express skepticism that the actual threat point is much further away. Both perspectives distance themselves from the claim that current hardware can immediately break BTC and ETH.

The U.S. National Institute of Standards and Technology (NIST) has advised organizations using public key cryptography to transition to quantum-resistant cryptography now. NIST has outlined a schedule to gradually remove quantum-vulnerable algorithms from standards by 2035. The focus of cryptocurrency networks is also on how to reduce the time it takes to transition compared to the hardware reach point.

For domestic investors, the issue is not price outlook but storage structure. The burden of transition may vary depending on what signature systems and key management methods exchanges, custodians, wallet operators, and bridge operators use. The estimates of exposed public keys should be viewed as a risk range for prioritizing transitions rather than as immediately stealable amounts.

The Google paper, Ethereum's official documentation, and the NIST schedule all point in the same direction. Quantum attacks are not an immediate concern today, but transitioning cryptography is not a task that can be completed in a day. Ethereum has set a target for 2029, and NIST plans to gradually remove quantum-vulnerable algorithms from standards by 2035.