files are sharded and hashed then digitally signed by the owner. Next they are broadcasted to the ftree network. Nodes compete with a short POW to store the next shard (the POW is to create randomness not earnings). When shards are retrieved an audit is run to see how many healthy shards are available. if less then 3 copies are found a new shard is automatically created on a another cell. Only one healthy shard is all that is required but 3 are always maintained.
No nodes are trusted they just store shards. To recreate a file you need to have the shard map (the list of the sha256 hashes for each shard). If you want the shards encrypted your client encrypts before the file enters the network and only you can decrypt it with the cypher you stored it with.