4 ms·

I’m not sure you appreciate how large that data structure would be if you had to ship it inside the app.

by kstrauser 1y ago

JustFinishedBSG 1y ago
I'm sure shipping a >150GB file to every user is perfectly fine and sound engineering.
- VWWHFSfQ 1y ago
  It's not _that_ far off from shipping a 3GB chrome webapp disguised as a desktop app (cough electron)
  - kstrauser 1y ago
    What’s a couple orders of magnitude between friends?
- NicolaiS 1y ago
  Parent comment writes: "ship[ing] the tree root hash", for a merkle tree ("bitcoin style") this would just be a single (small) hash no matter the tree size, i.e. 32 bytes is enough.
CodesInChaos 1y ago
The idea is to only distribute the root of the tree to a client, query the server for the username you want to look up, which then returns the key and a short proof that this username maps to that key within the hash tree identified by the known root.
- kstrauser 1y ago
  How is that substantially better than an API that returns a user’s key?
  - londons_explore 1y ago
    If the service provider (ie. the X.com servers) are evil, then the API can return false data and the client has no way to know. However, with a merkle tree, the root hash is embedded into the app, and the servers return the data together with info chaining to the merkle root (typically a few kilobytes, even if the whole tree is hundreds of gigabytes). With that info, the app can verify the chain to the root and be sure that the servers aren't returning false data.
    - fc417fc802 1y ago
      To clarify the above. It protects against endpoint compromise but depends on the assumption that the service operator (the one computing the root hash) is trustworthy. In other words it significantly reduces attack surface.
londons_explore 1y ago
It can be done with Merkel trees. You just ship the root hash. Merkel trees are snapshot/read only though - so you then use a bitcoin style Blockchain to ship refreshed versions of the root tree hash (you can even ship it in the actual bitcoin Blockchain if you like, piggybacking on its proof of work to ensure different people don't see different root hashes)

I’m not sure you appreciate how large that data structure would be if you had to ship it inside the app.

JustFinishedBSG 1y ago

I'm sure shipping a >150GB file to every user is perfectly fine and sound engineering.

VWWHFSfQ 1y ago
It's not _that_ far off from shipping a 3GB chrome webapp disguised as a desktop app (cough electron)
- kstrauser 1y ago
  What’s a couple orders of magnitude between friends?
NicolaiS 1y ago
Parent comment writes: "ship[ing] the tree root hash", for a merkle tree ("bitcoin style") this would just be a single (small) hash no matter the tree size, i.e. 32 bytes is enough.

CodesInChaos 1y ago

The idea is to only distribute the root of the tree to a client, query the server for the username you want to look up, which then returns the key and a short proof that this username maps to that key within the hash tree identified by the known root.

kstrauser 1y ago
How is that substantially better than an API that returns a user’s key?
- londons_explore 1y ago
  If the service provider (ie. the X.com servers) are evil, then the API can return false data and the client has no way to know. However, with a merkle tree, the root hash is embedded into the app, and the servers return the data together with info chaining to the merkle root (typically a few kilobytes, even if the whole tree is hundreds of gigabytes). With that info, the app can verify the chain to the root and be sure that the servers aren't returning false data.
  - fc417fc802 1y ago
    To clarify the above. It protects against endpoint compromise but depends on the assumption that the service operator (the one computing the root hash) is trustworthy. In other words it significantly reduces attack surface.

londons_explore 1y ago

It can be done with Merkel trees. You just ship the root hash. Merkel trees are snapshot/read only though - so you then use a bitcoin style Blockchain to ship refreshed versions of the root tree hash (you can even ship it in the actual bitcoin Blockchain if you like, piggybacking on its proof of work to ensure different people don't see different root hashes)