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@@ -1,6 +1,6 @@# Kela Kela is a new decentralized web protocol to make it easier for anyone to build and run decentralized web applications. It's basically a mishmash of ideas from ActivityPub, SMTP email, IPFS, BitTorrent, Nostr, the AT Protocol, and Spritely, but without the headaches of those existing protocols. Kela is a new decentralized web protocol to make it easier for anyone to build and run decentralized web applications. It's basically a mishmash of ideas from ActivityPub, SMTP email, IPFS, BitTorrent, RSS, Nostr, the AT Protocol, and Spritely, but without the headaches of those existing protocols. ## Motivation
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@@ -20,29 +20,8 @@ The DHT stores key-value pairs. The key consists of a user's public key and timestamp (the SHA-256 hash of the public key modulo 600 plus the current Unix time in seconds all divided by 600, rounded down). The value consists of a timestamp (the current Unix time in seconds), a list of servers that the user is associated with, where the first server is their primary server, and a signature. A key-value pair is assigned to the 5 servers with smallest SHA-256 hashes of their domain name greater than the SHA-256 hash of the key. The purpose of the elaborate timestamp in the key is to ensure that the set of servers assigned to a key-value pair rotates every 600 seconds so an attacker must control a very large portion of the DHT to do a denial-of-service attack against a specific key-value pair. When servers join and leave the DHT, the servers that a user is associated with will ensure that that user's key-value pair is assigned to a new server if necessary to ensure that 5 servers store that key-value pair. The DHT supports two operations, get and set. For set operations, the server checks the signature to ensure the validity of the request. When a server receives either of these two operations, it computes the SHA-256 hash of the key and checks if it is supposed to store that key-value pair or not. If it is supposed to store that key-value pair, it performs the operation on that pair. Otherwise, the server will contact in parallel the 5 servers that store this key-value pair. If the operation is a get, the server will look at the 5 replies and return the value with the most recent timestamp. If the operation is a set, and one of the 5 parallel requests fails, the server will remove that offline server from its DHT node list and assign a new server to this key-value pair to replace the offline one. Each server periodically goes through its stored key-value pairs and deletes old ones.The storage service uses a weaker form of primary-backup replication. The storage service supports the three operations get, set and delete, and a user's primary server always handles operations. Get operations are trivial. For a set or delete operation, the primary makes the modification and notifies all the backups about the operation, but responds to the user immediately without ensuring that the backups have performed the operation. All operations are stored in a log, which only stores the operation type and filename of the modified file, but not the contents of the operation. The log and files are persisted to disk. If a backup is offline, the primary maintains a log of all pending operations to be sent to the backup and will keep retrying. If the primary is offline, no progress can be made, but the user can designate any of the backups as the new primary, which also requires a set operation to the DHT to update that user's list of servers. When a backup becomes a primary, it must ensure that any other backups that are ahead of this one rollback their operations to match this backup. To rollback a delete operation, a backup can contact the new primary to get the file. The messaging service allows you to send arbitrary HTTP requests to other users. These messages are ephemeral. If the recipient is not online, then the message fails. In Kela, applications are users too and have a public key. They are functionally equivalent to automated users. OLD STUFF: ## Applications In Kela, applications and bots are the same thing. Just like users, applications have a public key, and are functionally equivalent to bots or automated users. You can tunnel HTTP (no TLS needed!) over Kela to host websites. Kela supports tunneling arbitrary data. Even better, Kela can replace your website's authentication system so you don't need passwords anymore! ## Examples ### Messaging app Let's try building a simple messaging app with Kela. First, create a folder on Kela's storage system, and share it with the person you are messaging. Then, both people can add messages to the folder. Of course, the low-level details here can be abstracted away by a GUI. The messaging service allows you to send arbitrary signed HTTP requests to other users. These messages are ephemeral. If the recipient is not online, then the message fails. In Kela, applications are users too and have a public key. They are functionally equivalent to automated users. To host a website over Kela, you can create an application and make that application listen to incoming messages and tunnel them over WebSockets to a website hosted locally on your computer. Even better, Kela can replace your website's authentication system so you don't need passwords anymore! If you want to build a messaging app using Kela, you need a different design, kind of like RSS. Basically, you have a file containing messages that you have sent to the other person, and they periodically fetch that file to see your messages. ## History A [few core ideas](https://social.exozy.me/@ta180m/108201791226634267) for Kela were braindumped by [Anthony Wang](https://a.exozy.me) on the fediverse in April 2022 and written down in a [repository](https://git.exozy.me/a/Kela/src/commit/a2561afe554382ae4ba9fcd9beb276497127dc3c). A few months later, Anthony Wang and [Alek Westover](https://awestover.github.io) developed a very basic [prototype](https://git.exozy.me/a/HackMIT) during [HackMIT 2022](https://hackmit.org). The name "Kela" comes from spelling "Alek" backwards. A [few core ideas](https://social.exozy.me/@ta180m/108201791226634267) for Kela were braindumped by [Anthony Wang](https://a.exozy.me) on the fediverse in April 2022 and written down in a [repository](https://git.exozy.me/a/Kela/src/commit/a2561afe554382ae4ba9fcd9beb276497127dc3c). A few months later, Anthony Wang and [Alek Westover](https://awestover.github.io) developed a very basic [prototype](https://git.exozy.me/a/HackMIT) during [HackMIT 2022](https://hackmit.org). The name "Kela" comes from spelling "Alek" backwards. The current design and implementation was written by Anthony Wang and Daniel Wang for a project for the [MIT Distributed Systems class](https://pdos.csail.mit.edu/6.5840/index.html).
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