gistfile1.txt

I understand that there's the ability to build a cluster with ipfs-cluster, with friends. But this is a shared storage space (everybody can delete stuff - not very good).

How about adding the ability to add peers as friends to a list, and give them the ability to store a given amount of bytes on my hard drive?

This could create a Web of Trust.

When the friend will pin a file, the file can be sharded and replicated according to his specifications to his list of peers - I will get also some parts of the file.

To acknowledge (somewhat reliably) that a "friend" peer still holds the data, he can be asked like once a day to XOR a salt to the file and send me the checksum. A list of salted-checksums can be calculated before seeding, avoiding that the data has to remain "local" to ask the nodes that they still hold our chunks reliably.

To avoid that a peer can read the data, the files could be preprocessed to just send every n bit to a given peer, that the peer ends up with scrambled data which cannot be used without having data from other peers. This doesn't replace true encryption - but is extremely cheap to do on a CPU and has the advantage that changed content may be transmitted via diff updates.

The user should be asked if he wants to scramble, encrypt or share the data plainly.