Key Highlights
- Ethereum is building a Post-Quantum Public Key Registry to protect validator security from future quantum computer attacks.
- It is moving from BLS signatures to XMSS, a hash-based system that is simpler, more trusted, and resistant to quantum threats.
- The upgrade includes SNARK-based compression and a gradual rollout to keep the network scalable and stable during the transition.
Ethereum is working on a major upgrade called a Post-Quantum Public Key Registry, designed to prepare the network for a future where quantum caomputers could break today’s crypto security.
The update was shared on X by Ethereum researcher Thomas Coratger, who cited a report confirming that he and fellow researchers Tom Wambsgans, Ladislaus, Thomas Thiery, and Justin Drake are leading the idea.
The proposal is part of the network’s long-term plan to protect its validator system from future attacks and make the network safe for many years to come.
Why Ethereum is preparing for quantum risk
According to the report, Ethereum currently uses a proof-of-stake system called BLS12-381 signatures for validators. These signatures help confirm transactions and secure the network.
But there is a problem. These systems depend on elliptic curve math, and powerful quantum computers could break them in the future using special algorithms like Shor’s algorithm. Because of this risk, Ethereum is planning a careful switch to a safer system before that future arrives.
The first step: Public key registry
The first step is a Public Key Registry. According to the report, the registry allows validators to register new post-quantum keys before they are actually used in the main system.
This is important because it separates “saving the key” from “using the key in real security work.” It gives validators time to adjust their systems slowly, instead of forcing a sudden change.
The transition will reportedly happen in stages. First, the registry will be added. Later, after more testing and upgrades, the new signature system will fully replace the old one.
XMSS: The new security core
The research team said the new security system uses XMSS (eXtended Merkle Signature Scheme), a type of hash-based signature system. It does not rely on complex math like other post-quantum ideas. Instead, it uses simple hash functions, which are much easier to trust and test.
As the research explains, hash-based signatures are chosen because they rely on basic rules like “collision resistance” and “preimage resistance,” which are well understood and very strong.
The team explained that XMSS works like a tree of many small keys. Each validator has a huge set of one-time keys stored as leaves in a Merkle tree. The top of this tree becomes the public key. Every time a validator signs something, it moves to the next leaf. This means each key is used only once, which helps prevent attacks.
Built-in protection against cheating
The system also has a built-in defense against cheating. Messages are split into parts and must follow a strict rule called a “target sum.”
If someone tries to change one part of a signature, they must adjust another part. But because hash functions cannot be reversed, it becomes impossible to cheat the system without breaking the rules.
Size, scaling, and network efficiency
Furthermore, each validator’s public key is very small, only 52 bytes. It contains a 32-byte Merkle root and a 20-byte parameter. Even if Ethereum had one million validators, the total extra storage would only be about 52 megabytes. However, each XMSS signature is about 3.1 KB, which is much larger than current BLS signatures, so extra compression methods are required.
To fix this, Ethereum plans to use a compression method using SNARK technology through a system called leanVM. This can bundle many signatures into a single proof of about 128 KB, making it easier for the network to handle. Without this, network traffic would reportedly become too heavy for each slot.
Gradual rollout for network safety
To manage rollout, the team said the system will limit how many validators can register per block with suggestions like 16 per slot.
Early participation will reportedly get rewarded, while delayed validators may be pushed to upgrade. This slow and steady rollout is meant to keep the network stable while moving toward full quantum safety.
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