But in my setup, somebody with access to the frontend server could not decrypt the private keys because they were pgp encrypted, and the pgp private key wasn't stored on the frontend. The aes pass wasn't stored on the mysql server, tech guys from the hosting firm did't have my root pwd, and if they would have rebooted my machine to reset the root pwd, they would have been faced with an encrypted disk... However, my weak point was the server where the core wallet was stored since it had to have access to the private keys in order to handle outgoing payments so it needed to be on the same vlan as the mysql server with one interface, and it needed both the pgp pk and the aes password
I am having the same concept but the weak spot will be the API server who knows the private key for decrypting the bitcoin private key.
when i read about the latest and biggest hacks, actually most of them started with infected hardware from an admin. i think maybe protecting the server is one thing (offline, whitelist IP access, no SSH access to DB and Web application firewall) but for example bitstamp, all of this would not have helped as far as i know.
multi sig is the solution, yes, but when 1 server is compromised, most likely the others are too.