Bitcoin, Ethereum diverge on post-quantum defenses

Bitcoin and Ethereum are pursuing different technical paths to address the future risk posed by quantum computing. Bitcoin’s community favors incremental changes that limit exposed public keys, while Ethereum is planning multi-layer upgrades to enable swapping cryptographic primitives when needed.

Bitcoin developers have focused discussion on proposals such as BIP-360, which would introduce Pay-to-Merkle-Root (P2MR) outputs. P2MR changes transaction output formats to reduce how often public keys appear on-chain, without replacing the underlying elliptic curve primitives. Proponents say the change aims to preserve backward compatibility and keep protocol behavior predictable while reducing immediate exposure.

Ethereum’s developers are formalizing a roadmap that targets cryptographic agility across the execution, consensus and data layers. Work under consideration includes account abstraction and alternative signature schemes on the execution layer, different validator signature mechanisms on the consensus layer-including hash-based approaches-and adjustments to data availability and storage formats on the data layer. The plan emphasizes staged changes and testing before broader deployment.

Both networks rely today on elliptic curve cryptography for signatures. Quantum algorithms such as Shor’s algorithm could, in theory, derive private keys from exposed public keys. The risk is concentrated where public keys are visible on-chain: addresses that have already spent funds and revealed their public keys are more exposed than unused addresses. Wallet practices that avoid address reuse reduce the number of exposed keys.

Public-sector and corporate timelines have added urgency to the discussion. In March 2026 Google announced a target to move its systems to post-quantum cryptography by 2029 and warned that future quantum machines could threaten existing encryption and signatures. That timeline has prompted organizations that rely on long-lived cryptographic protection to ask blockchain projects for mitigation plans.

Both ecosystems face technical and coordination challenges. Migrating assets secured by legacy keys requires methods to move value without exposing private keys. Decentralized governance complicates timing and scope for protocol changes because upgrades need broad agreement among diverse participants. Any change must weigh backward compatibility against the need for stronger cryptography.

The approaches reflect differences in design and governance. Bitcoin’s base-layer design emphasizes stability and a high bar for consensus, encouraging slower, conservative modification. Ethereum’s development process has delivered coordinated, large-scale upgrades in the past and is organizing a longer-term transition plan for cryptographic agility.

Neither Bitcoin nor Ethereum has adopted a final, network-wide post-quantum solution. Developers, researchers and node operators continue to test proposals, model migration scenarios and assess trade-offs while work on standards and tooling proceeds.