- An encrypted key which is owned by both coinbase and the user.
Which I supposed they can decrypt? Can't they? What is the point of an encrypted key in the first place if the user cannot decrypt it?
Right. OP has the encryption password and he/she should be able to decrypt the shared key, but the question is how the key should be decrypted, what's the encryption algorithm and what tool should be used for that.
Also, I am not even sure if the user share OP is talking about is a master private key.