Aes with ecdh
Isnt that what the encrypted private keys in bitcoin use?... Its based on encrypting the private key based on a phrase..
Ecdh is a secure key exchange algo, Secure key exchange algorithms are used to exchange our keys securely via a non secure channel.
ECIES is an Integrated Encryption scheme, it.is a hybrid encryption scheme which provides semantic security against chosen plain text and chosen cipher text attacks.
For memos you would use ecies not ecdh if you using existing keypairs from bts
If you need to prove the sender sent the message use ecdsa for this