Ethereum Prepares for Quantum Threat with New Deposit Contract Proposal

Ethereum developers have proposed a new deposit contract plan to prepare for the threat of quantum computers breaking signatures. The proposal, filed under EIP-9999 in the GitHub repository, aims to process variable-length public keys and authentication data.

The current Ethereum deposit contract assumes fixed BLS12-381 public key and signature sizes, making it unable to accept larger post-quantum keys. The new contract structure assigns an identifier called a 'schema' for each deposit, with Schema 0 referring to existing BLS signatures and other values reserved for future assignment.

The proposal also includes a phased shutdown procedure for the BLS method. It starts in an invalid state that rejects deposits immediately after introduction, then accepts the existing BLS method in an operational stage. In the final stage, it moves to a deprecation state that stops new BLS submissions.