[jerguismi]

Different key. The other key is encrypted with BIP38 with your chosen password. I don't know how the actual interface works, if it is encrypted client-side or server-side. Anyway, on paper it sounds fantastic.

[adrianmacneil]

Yes, the shared key is generated and encrypted with your passphrase client-side, then sent to Coinbase. We never see the raw private key.