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|blake
POST /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 🤷
It’s quite simple: I want to
retrieveFile(fileHash)
wherefileHash
is the output ofmd5sum $file
orsha256sum $file
, or whatever other hashing algorithm exists.This seems like a restatement of X. We still don’t understand Y. I’m especially confused about:
There was some hint that maybe you’re concerned about reproducibility for CIDs? If you fix the block size, hash algorithm, and content codec you’ll get consistent results. SHA-256 also breaks data into chunks of 64 bytes as it happens.
Anyway Wikipedia has a list of content-addressable store implementations. A couple that stand out to me are git and git-annex.