Account Abstraction as a Path to Sunseting ECDSA on Ethereum?

A future version of Ethereum is expected to support an account abstraction, a unified representation of an account (rather than the two types that exist today; a smart contract account, and an externally owned account (EOA) with a corresponding ECDSA private key). The most recent account abstraction proposal under consideration is EIP-4337. Among its features is a representation of an account as a smart contract wallet with cryptographic agility for submitting requests (referred to as UserOperations) to the wallet. UserOperations can be signed using a quantum safe signature scheme. Under this proposal, after a network upgrade, the current user base with quantum vulnerable EOAs “can individually upgrade their wallets to quantum-safe ones”, as noted by Vitalik.

In the event of a quantum attack breakthrough, the user dependent upgrade strategy might mean a large number of unconverted accounts. Addresses with prior transaction history would be at highest risk. A recent Deloitte study examining addresses holding ether found that 65% of these addresses have a prior transaction history, where the ECDSA public key can be readily retrieved (this is excluding ERC20s tokens and other forms of assets). If the quantum attack breakthrough occurs while any significant portion of EOAs haven’t been upgraded yet, any subsequent transactions signed with ECDSA (including upgrade to quantum resilient wallet) would be suspect: is it the attacker or the key rightful owner performing the operation? By comparison, this dilemma is more severe than the Ethereum rollback debate after the 2016 DAO exploit (which resulted in a hard fork, and two chains going forward, Ethereum and Ethereum classic). To address this problem, a path rooted in cryptographic based trust is needed even when the algorithm authorising the majority of today's transactions is compromised (i.e., in a scenario where users need to migrate their Web3 assets to a forked version of the chain, where UserOperations only use quantum resilient algorithms).