As the title say, is it possible to restrict access to files stored on Filecoin? I briefly looked through the documentation and did not find anything on this. I am thinking of a use case where companies store their data on filecoin but need to know if it is different from IPFS where files are by default public and accessible to anyone.
There is no permissioning or encryption built-in to the Filecoin protocol, which allows it to be more flexible for storage client developers to add their own.
Retrieval in Filecoin requires 1) the Miner ID and 2) Payload/Data CID (same CID as in IPFS). Adding the Payload/Data CID to a storage deal’s metadata on chain is optional - this can be turned off in a Filecoin Lotus node. If not included, then only the Storage Client and Miner would know the Payload/Data CID for retrieval.
The Retrieval Market is currently a basic version and will evolve and I think these kinds of access questions will have good solutions in the future.