http://protonmailrmez3lotccipshtkleegetolb73fuirgj7r4o4vfu7ozyd.onion/blog/centalized-vs-p2p-protondrive
Our centralized servers hold the encrypted data, but the decryption keys are tied to user passwords that we do not know. The resistance of any system to hacking is based on the security measure it uses. If a hacker can compromise a system, then it matters little if the system is centralized or decentralized.