Ethereum Researcher Outlines Post-Quantum Account Protection for $0.07 Without a Hard Fork

Nicolas Consigny, a researcher with the Ethereum Foundation working on the Kohaku privacy project, has published a method that lets Ethereum accounts add quantum-resistant protection for roughly $0.07 each without waiting for a hard fork. The approach treats post-quantum security as something a user can adopt voluntarily at the account level rather than a network-wide upgrade requiring consensus.

The technical core is an adaptation of SPHINCS+, a hash-based signature standard already selected for post-quantum use, into a variant Consigny calls SPHINCS-. Because the scheme is built entirely from hash functions, replacing the standard SHAKE256 hash with Ethereum's native KECCAK256 opcode makes on-chain verification possible without new precompiles or protocol changes. Verification runs at about 150,000 gas using existing infrastructure.

Delivery relies on account abstraction. Using the ERC-4337 standard, an account can swap in the post-quantum signature scheme on its own, which is why no fork is needed. Consigny frames SPHINCS- as a transitional measure until Ethereum ships longer-term upgrades such as leanSPHINCS, which would aggregate signatures to cut costs further.

The proposal matters because it separates the timeline of the quantum threat from the slow cadence of protocol governance. If a credible quantum attack on elliptic-curve signatures ever arrives, users who upgraded early would already hold accounts that do not depend on the vulnerable scheme.