inb4: IPFS doesn’t work, unfortunately as you cannot provide the hash of an arbitrarily large file and retrieve it from the network. IPFS content IDs (CID) are a hash of the tree of chunks. Changes to chunk size can also change the hash!
Basically, I’d like to take the SHA256, SHA3, blake2, md5, of a file and either retrieve it from a network or get a list of sources for that file. Does something like that exist already or will I have to build it?
If I have to build it
it will be a really simple, dumb, HTTP service with
GET /uris/:hash:?alg=sha256|md5|blakePOST /uri/:hash:with the contents being a URI to the file
supported URI schemes would probably be HTTP/S and FTP. Maybe P2P protocols like IPFS and if there’s a way to target a specific file in a torrent, maybe magnet links too. But that’s feels like risky territory.
Of course for hashing requests it would have a limited task queue (maybe 5 in parallel?), rate limiting by IP, and a size limit for retrieval (1GB feels like more than enough).
Can’t think of a way to do it with a DHT 🤷
Blake 3 supports verified streaming as it is built upon merkle trees as you described. So is IPFS. As I mentioned, IPFS hashes are that of the tree, not the file contents themselves, but that doesn’t help when you have a SHA256 sum of a file and want to download it. Maybe there are networks that map the SHA256 sum to a blake3 sum, an IPFS CID, or even an HTTP URI, but I don’t know of one, hence the question here.
Do you know of a way to exploit that? A library maybe?