New EIP Draft Would Run Post-Quantum Signatures Alongside BLS

A draft EIP posted to Ethereum Magicians on November 12, 2026, proposes running a post-quantum signature aggregation scheme called leanVM alongside Ethereum's existing BLS consensus signatures — without giving leanVM any authority over block validity — until a defined trigger point the draft calls "PQ/AI day."

What the draft actually proposes

Per the draft posted by the Ethereum Magicians account, consensus validity would continue to depend on BLS alone, "exactly as today." leanVM would run in what the authors term "shadow mode": its aggregates and proofs would be produced and verified in parallel with BLS, but only measured, compared, and reported — not acted upon. The draft states that when "PQ/AI day" arrives, "an emergency hard fork simply retires BLS and enables leanVM in full."

The draft defines "PQ/AI day" as the point at which quantum computers, or AI-assisted cryptanalysis, make BLS unsafe to rely on. The proposal does not set a calendar date for that trigger; it frames the shadow-mode period as a monitoring and testing phase rather than an immediate cryptographic transition. BLS signature aggregation underpins how Ethereum validators attest to blocks under its current proof-of-stake consensus design, and any replacement scheme has to prove itself under live network conditions before it can be trusted to carry consensus weight alone.

Why shadow mode matters for a live consensus layer

Running a new cryptographic scheme in shadow mode — producing output without consensus authority — is a common pattern for introducing high-stakes changes to a live blockchain without risking a chain split or validation failure if the new scheme has an undiscovered flaw. The draft's structure means leanVM would need to demonstrate it can track BLS reliably across real validator activity before its proofs are given any binding weight.

The proposal does not specify a timeline for moving from the current draft stage to a shadow-mode deployment, nor does it name which client teams or researchers beyond the posting account are currently reviewing it. As an Ethereum Magicians forum post, it represents an early-stage draft EIP rather than an adopted standard — proposals posted to the forum typically go through extended community discussion, specification revisions, and client implementation work before reaching a position where core developers would consider them for inclusion in a scheduled upgrade.

What happens next depends on review activity on the forum thread itself and whether client teams pick up the proposal for prototyping. CoinsCipher will track the thread for updates on implementation timelines or formal EIP numbering.