I have close to 100K in bitcoin in different accounts. I own some in Coinbase. I am planning to borrow around 60 to 70K USD as a loan for 1 year. I prefer to borrow as a interest-only loan, where I pay 1/12th of the interest every month.
Coinbase changes the public key of the wallet. It is not letting me sign messages. If you like to confirm that I have BTC collateral in my account, I can show a screenshot from my Coinbase account.
https://drive.google.com/open?id=0Bw5Ltg6CklBydnZoaHE5MlI0LWc If you are interested, please PM me.
Roughly Right
Coinbase allows me to sign messages just fine, even if the public key changes, you can go into your history, select detail, click sign a message, and sign a message with that address, and if you cannot prove with a sign message you do not have $100k worth of btc until otherwise proven, and no sane person would hold that much coins in a online exchange either.
You better off locking this thread before you get a negative trust because no one is going to believe you, and screenshots can be altered as well