Ordinary accounts controlled by a single private key.
The idea: The account is just a key pair: whoever can produce a valid ECDSA signature with the private key controls the funds. There's no recovery and no way to swap in a different kind of key. Even with EIP-7702 delegation, the original key keeps full control. That's why moving to quantum-safe signatures needs new account types or a protocol change.
Why it matters: They hold most ETH, and once they've signed a transaction they're exposed to future quantum computers.
On the map: any account that has sent a transaction has exposed its public key to quantum attack
Externally owned accounts, ordinary accounts controlled by one private key, hold most ETH and tokens. Each transaction is authorized with an ECDSA signature[1], and the address is a hash of the public key.
Every account that has sent a transaction has revealed its public key (it can be recovered from any signature), so a future quantum computer could derive its private key. Accounts that have only received funds are protected by the address hash until they first sign.
If any of these breaks, this breaks too.
If this breaks, these break with it.
Nothing on the map depends on it: it is an end point, something people use directly.
Next-step links, not dependencies: these don't fall together.