Ethereum plans to revolutionize cryptography for future verifiers

Ethereum experts propose to rebuild deposit contracts to prepare for anti-quantum signatures.

Ethereum experts have released a proposal to rebuild contracts that allow verifiers to deposit ETH. The purpose is to introduce a new cryptographic system to replace the currently used BLS signatures. Nearly 42.4 million ETH (worth approximately US$104 billion) rely on this format. The proposal is still a working draft and has not yet selected any post-quantum algorithms and fails to ensure that the network is protected from any attacks.

New contract will support multiple cryptographic key formats

Current BLS signatures will temporarily remain compatible. An irreversible mechanism will then block new BLS deposits. There is currently no quantum computer that can break Ethereum. Current deposit contracts hinder any rapid migration.

On August 24, three researchers submitted a deposit contract proposal for Ethereum validators. Specifically, Kevaundray Wedderburn, Tom Wambsgans, and Thomas Coratger want to prepare a pledge system for the future adoption of signatures that are resistant to quantum computers.

It should be pointed out that deposit contracts are the entrance to pledge. Investors lock in ETH here, before its verifiers can join the network, verify transactions, and participate in consensus. Current processes accept fixed-size public keys and BLS signatures.

The BLS public key used by Ethereum takes 48 bytes and the signature size is 96 bytes. This configuration has significant advantages: multiple signatures can be merged and the size does not increase proportionally with the number of verifiers. As a result, Ethereum is able to efficiently perform the voting required for its beacon chain to operate.

However, this dependence may become a limit in future cryptographic migration. Post-quantum systems often use larger keys and signatures. As a result, even if researchers immediately agreed on alternative algorithms, current contracts would have difficulty accepting them without modification.

This difficulty affects a large part of the ecosystem. Currently, approximately 42.4 million ETH pieces are pledged, worth approximately US$104 billion. The funds are not currently threatened, but the cryptography used by the validators who ensure their security will become fragile in the long term.

Identifiers will allow switching cryptographic systems

Contracts submitted by developers can accept variable-length public keys, signatures, and metadata. Therefore, each deposit will also contain an identifier that specifies the cryptographic system used by the verifier. The number 0 will be reserved for the current BLS format to ensure compatibility during the transition.

Future identifiers may be compatible with post-quantum signatures or other schemes still under development. This structure may bring a kind of cryptographic flexibility to Ethereum. Blockchain will be able to add new architectures without having to rebuild the entire deposit contract.

However, the proposal does not intend to select a post-quantum algorithm, it simply designs the infrastructure that can accommodate such algorithms. New protocol modifications will be needed in the future to define verification, aggregation and processing rules for new signatures at the consensus level.

Various deposit data may also be transmitted through execution layer requests. The mechanism introduced by EIP-7685 ensures the transfer of certain operations from the execution layer to the consensus layer. It is worth noting that Ethereum has used it for deposits, withdrawals from execution, and validator mergers.

This change will replace the historical architecture based on the Merkel Tree and integrate future post-quantum deposits into the structure already used for multiple pledge-related operations.

Ethereum may permanently close the BSL deposit channel

Multiple migrations may follow. The contract will first accept BLS deposits while gradually incorporating a new signature format. This will give Ethereum clients, validators and pledge operators time to adapt various tools.

Future protocol decisions will help disable new deposits using the BLS system. In the current version of the proposal, this mechanism may be irreversible. When this mode is activated, verifiers will no longer be able to join Ethereum using the old format key.

Activated BLS verifiers will not be removed immediately due to this shutdown. In fact, additional rules are needed to manage key migration, exit, or change to withdrawal identifiers. Therefore, this document is mainly aimed at the addition of future validators rather than the comprehensive migration of existing operators.

Such proposals do not consider user wallets. Verifiers rely on BLS, while regular Ethereum accounts use ECDSA signatures. Accounts, KZG commitments for data, and certain zero-knowledge proof systems all require their own post-quantum solutions.

Because of this difference, the new contract cannot be regarded as universal protection for Ethereum. It is just part of a broader migration involving multiple layers of the protocol and its extensive infrastructure.

Comprehensive protection is expected around 2029

The Ethereum Foundation has established a dedicated post-quantum security team in January this year. Its official action plan aims to gradually implement key protection measures during 2029. This time point is still a planning goal and not a guaranteed date.

In order to modify the BLS signature, developers are studying leanXMSS. This is a system based on a hash function and is believed to be resistant to quantum attacks. However, its signature is much larger than currently used signatures, causing bandwidth and processing problems.

This growth must be made up for through the LeanVM project. This specialized virtual machine can prove the aggregated quantum signature through cryptography. EIP-8292 proposes leaving this task to aggregators with the necessary hardware without imposing a burden on all individual verifiers.

The infrastructure itself needs to be designed with new trade-offs. The aggregator will be able to generate proof very quickly because its computing power far exceeds that of individual pledgers. Therefore, researchers need to prevent such functions from exacerbating network centralization.

Current threats do not come from quantum risk. The official Ethereum document points out that there are currently no quantum computers that can break the network's cryptographic system. Users and verifiers do not require urgent action.

The proposal now requires the publisher's consent, technical discussions, formal numbering, and inspection through the EIP warehouse. It then needed to be implemented, audited, and tested on the client side, and was finally selected for inclusion in future hard forks. Until these steps are completed, the new contract is only preliminary preparation rather than proactive protection.