I'll just leave this here. There are some notes I quickly jotted into my phone. Let me know if there is interest in this, and I'll type something up that more closely resembles actual prose.

Related-To: #203 #63 #65

• Replace user/pass with public key identity.

• Every user is their key fingerprint.

• Key is optionally and by default kept on the server, passphrased.

• Client keeps a local copy of the key, if possible, allowing for account recovery in case server loses the key blob.

• Server never sees the passphrase - private key is downloaded from the server by the client, decrypted with the passphrase, and used to sign in. (*Need some mechanism that prevents downloading all key blobs from HS, possibly use an alternative s2k algorithm on the passphrase to unlock download.)

• Also clears the way for true account migration. (Link in spec leading nowhere #712)

• On joining a room, send a BIND_HS message to bind the decentralized ID to the homeserver and local identity.

• On migrating an account, the same BIND_HS can be sent to change the homeserver.

• A given decentralized ID can only exist on one HS at a time (per room).

• The e2e keys could be signed with the account key, providing a single identity for all a user's devices, including future devices.