Ethereum is preparing to transition to post-quantum cryptography, targeting around 2029.

Cointelegraph reported on Tuesday that while the threat has not yet materialised, Ethereum has judged it cannot delay a response.

Ethereum's current cryptographic system is secure in conventional computing environments. But once sufficiently advanced quantum computers emerge, private keys could be exposed and billions of dollars in value could be put at risk. Ethereum sees no immediate threat, but views upgrading a global decentralised network as a multiyear task requiring protocol redesign, ecosystem-wide coordination and broad verification.

The sticking point is performance degradation. Post-quantum cryptography often comes with larger signature sizes and heavier verification workloads than existing signature methods. Many approaches also do not provide efficient aggregation as a built-in feature, like the BLS signatures used by Ethereum's consensus layer.

The burden could be most pronounced in the consensus layer. Today, proofs from thousands of validators are efficiently aggregated with BLS signatures, keeping bandwidth use low, verification fast and scalability intact. Simply swapping this for a heavier alternative could slow block propagation and increase the burden on validators, reducing overall efficiency.

Ethereum has chosen structural redesign rather than a simple replacement. The core is SNARK-based aggregation. It verifies a single compressed cryptographic proof instead of checking thousands of heavy proofs individually. In the execution layer, gas costs could rise somewhat as signature verification becomes more complex, and Ethereum is also reviewing wallet design changes using account abstraction and a phased transition.

Strain on the data layer is another variable. Larger cryptographic elements could add pressure to data availability systems and blob storage, and could also complicate network propagation. Rather than locking in prematurely to a specific solution, Ethereum is prioritising cryptographic agility that would allow it to change algorithms when needed.