Ethereum developers have proposed a significant redesign of the validator deposit contract to help protect the network's multi-billion-dollar staking layer from future quantum computing threats. Submitted as a draft Ethereum Improvement Proposal (EIP) on Monday, the measure is the network's first concrete move toward post-quantum cryptography.
The existing deposit contract currently hardcodes the dimensions of the BLS12-381 signature scheme, fixing public keys at 48 bytes and signature metadata at 96 bytes. Because post-quantum cryptographic schemes require substantially more data space, the current contract lacks the necessary capacity.
The proposed replacement contract would accept keys and credential metadata of up to 8,192 bytes each. It requires every deposit to declare its specific credential scheme, with scheme zero designated for the current BLS approach. The draft does not define specific post-quantum keys, leaving those standards to be established by a future EIP.
To manage the transition, the contract operates in three modes: disabled, BLS enabled, and BLS retired. Once a system call shifts the contract into the retirement mode, no subsequent call can re-enable BLS onboarding, and new deposits signed with the current BLS scheme are permanently blocked.
The proposal transmits deposit data to the consensus layer while leaving the underlying cryptography to be defined later. Implementing the change would require a coordinated hard fork across both the execution and consensus layers.
As a draft awaiting review from EIP editors, the proposal still leaves several elements undecided, including its deployment code, contract addresses, and activation timestamps. Co-author Thomas Coratger highlighted the complexity of the underlying cryptography, noting that post-quantum cryptography is not a simple upgrade.
According to Coratger's recent commentary referencing a talk by Stanford cryptographer Dan Boneh, both Ethereum and Bitcoin are leaning toward stateless, hash-based signatures standardized by NIST that require approximately 8KB each—matching the new contract's size ceiling.
The Ethereum Foundation previously formed a dedicated team to plan the network's post-quantum transition. Meanwhile, a May report from quantum security firm Project Eleven estimated a better-than-even probability that a machine capable of breaking elliptic curve signatures will emerge by 2033, with 2030 also considered possible. The analysis noted that more than 65% of all ETH is held in addresses with public keys already exposed onchain.
