Veilid Concepts

Now that we know what Veilid is and what we intend to put on it, the second order of business is to address the parts of the question of how Veilid achieves that. Not at a very detailed level, of course, that will come later, but rather at a middle level of detail such that all of it can fit in your head at the same time.

Concepts covered in detail include:

• Nodes
• The Distributed Hash Table
• Bootstrapping
• Cryptography
• NAT Traversal
• Private Routing

Here's a little overview to get things started:

Peer Network for Data Storage

The bottom-most level of Veilid is a network of peers communicating to one another over the internet. Peers send each other messages (remote procedure calls) about the data being stored on the network, and also messages about the network itself. For instance, one peer might ask another for some file, or it might ask for info about what other peers exist in the network.

The data stored in the network is segmented into two kinds of data: file-like data, which typically is large, and textual data, which typically is small. Each kind of data is stored in its own subsystem specifically chosen to optimize for that kind of data.

Block Store

File-like content will be stored in a content-addressable block store, a work in progress. Each block is just some arbitrary blob of data (for instance, a JPEG or an MP4) of whatever size. The hash of that block acts as the unique identifier for the block, and can be used by peers to request particular blocks. Technically, textual data can be stored as a block as well, and this is expected to be done when the textual data is thought of as a document or file of some sort.

Distributed Hash Table (DHT) Store

Smaller, more ephemeral textual content generally, however, is stored in a DHT store. Things like status updates, blog posts, user bios, etc. are all thought of as being suited for storage in this part of the data store. DHT store data is not simply "on the Veilid network", but also owned/controlled by users, and identified by an arbitrary name chosen by the owner the data. Any group of users can add data, but can only change the data they've added.

For instance, we might talk about Boone's bio vs. Boone's blogpost titled "Hi, I'm Boone!", which are two things owned by the same user but with different identifiers, or on Boone's bio vs. Marquette's bio, which are two things owned by distinct users but with the same identifier.

DHT store data is also stateful, so that updates to it can be made. Boone's bio, for instance, would not be fixed in time, but rather is likely to vary over time as he changes jobs, picks up new hobbies, etc. Statefulness, together with arbitrary user-chosen identifiers instead of content hashes, means that we can talk about "Boone's Bio" as an abstract thing, and subscribe to updates to it.

Structuring Data

The combination of block storage and DHT storage together makes it possible to have higher-level concepts as well. A song, for instance, might be represented in two places in Veilid: the block store would hold the raw data, while the DHT store would store a representation of the idea of the song. Maybe that would consist of a JSON object with metadata about the song, like the title, composer, date, encoding information, etc. as well as the ID of the block store data. We can then also store different versions of that JSON data, as the piece is updated, upsampled, remastered, or whatever, each one pointing to a different block in the block store. It's still "the same song", at a conceptual level, so it has the same identifier in the DHT store, but the raw bits associated with each version differ.

Another example of this, but with even more tenuous connection between the block store data, is the notion of a profile picture. "Marquette's Profile Picture" is a really abstracted notion, and precisely which bits it corresponds to can vary wildly over time, not just being different versions of the picture but completely different pictures entirely. Maybe one day it's a photo of Marquette and the next day it's a photo of a flower.

Social media offers many examples of these concepts. Friends lists, block lists, post indexes, favorites. These are all stateful notions, in a sense: a stable reference to a thing, but the precise content of the thing changes over time. These are exactly what we would put in the DHT store, as opposed to in the block store, even if this data makes reference to content in the block store.

Peer and User Identity

Two notions of identity are at play in the above network: peer identity and user identity. Peer identity is simple enough: each peer has a cryptographic key pair that it uses to communicate securely with other peers, both through traditional encrypted communication, and also through the various encrypted routes. Peer identity is just the identity of the particular instance of the Veilid software running on a computer.

User identity is a slightly richer notion. Users, that is to say, people, will want to access the Veilid network in a way that has a consistent identity across devices and apps. But since Veilid doesn't have servers in any traditional sense, we can't have a normal notion of "account". Doing so would also introduce points of centralization, which federated systems have shown to be a source of trouble. Many Mastodon users have found themselves in a tricky situation when their instance sysadmins burned out and suddenly shut down the instance without enough warning.

To avoid this re-centralization of identity, we use cryptographic identity for users as well. The user's key pair is used to sign and encrypt their content as needed for publication to the data store. A user is said to be "logged in" to a client app whenever that app has a copy of their private key. When logged in a client app act like any other of the user's client apps, able to decrypt and encrypt content, sign messages, and so forth. Keys can be added to new apps to sign in on them, allowing the user to have any number of clients they want, on any number of devices they want.