The problem is not that only authorized clients can write, that is the easy part (signatures are enough for that). The problem is limiting read access. Having

The problem is not that only authorized clients can write, that is the easy part (signatures are enough for that). The problem is limiting read access. Having a globally distributed db means that anyone can get a copy. You can use ipfs for public data, and to store private encrypted data (with caveats: make sure you change the encryption key/nonce for every data change). There is no way to modify private data depending on anonymous access without things like omomorphic encryption, and the whole system is completely void of any form of forward secrecy. As someone who works with encryption and security, I can not recommend storing anything private on distributed systems. Leaks way too much data, and there are too many caveats. You can have securely designed applications, but I see no way to safely port common websites completely on distributed infrastructure without leaking a lot of data that today is supposed to be kept secret.