A proposed Ethereum upgrade could allow validators to adopt quantum-resistant keys and eventually retire the BLS signature format currently used by the network.
Ethereum researchers have drafted changes to the deposit contract that lets users lock ETH and become validators, with the aim of protecting the blockchain against future attacks powered by quantum computing.
The proposal would modify Ethereum’s deposit contract, which acts as the entry point for users joining the validator set. Validators are responsible for confirming transactions and maintaining network consensus. The proposed changes would introduce a mechanism allowing Ethereum to eventually stop accepting the signature format currently required for new deposits.
Ethereum’s Existing BLS System Creates a Quantum Hurdle
The current deposit contract hard-codes the size of BLS cryptographic keys, making it difficult for Ethereum to introduce a different signature system. Even if developers agreed on a quantum-resistant standard, the existing contract could not accommodate it without first being redesigned.
Ethereum currently has around 42.4 million ETH staked, representing approximately $104 billion at current prices. The staked funds are secured by validator keys using the BLS format that the proposal aims to phase out over time.
The proposal is still under review and has not received a finalized EIP number. It is currently listed under a temporary identifier, with a repository maintainer suggesting EIP-8394 as a potential number.
The draft would also replace the original deposit-processing system introduced with Ethereum staking in 2022. The newer framework would handle deposits alongside the withdrawal and validator-management functions it already supports.
How the New Deposit Framework Could Work
Validators currently rely on BLS signatures to participate in Ethereum’s consensus process. BLS has an important efficiency advantage because it can aggregate large numbers of signatures into one, helping keep the cost of consensus manageable.
However, BLS depends on elliptic-curve cryptography that could theoretically be compromised by a powerful quantum computer using Shor’s algorithm. If that occurred, an attacker could potentially forge validator signatures.
Because the existing contract fixes the size of BLS keys, it cannot currently support alternative cryptographic formats. The proposed redesign would allow different key sizes and attach a tag to each deposit identifying the cryptographic system being used. BLS would receive tag zero, while future tags could be assigned to new signature schemes.
Initially, Ethereum could continue accepting BLS deposits while also supporting alternative cryptographic systems. Developers could later disable new BLS deposits entirely. Existing BLS validators would remain active, but anyone joining the validator set would need to use a supported alternative.
Ethereum would also need an additional protocol change to enable validators to verify signatures created with the new cryptographic systems.
Ethereum Prepares for the Quantum Era
The validator proposal is only one part of Ethereum’s broader quantum-resistance strategy. EIP-8141, known as the Frame Transactions proposal, is another initiative being considered for the Hegotá upgrade later this year.
Frame Transactions could allow standard Ethereum accounts to switch the cryptographic method used to authorize transactions without forcing users to move their assets to a new address.
The need for such upgrades became more pressing after Google Quantum AI research released in March identified five potential quantum attack vectors affecting Ethereum. The research indicated that more than $100 billion worth of assets could eventually be exposed across wallets, staking, smart contracts and layer-2 networks.
The Ethereum Foundation is working toward a target around 2029 for implementing the core protocol changes needed to make Ethereum more resilient against quantum-computing attacks.
