Swarm Channels, Namereg resolution draft

Channels and streams

a swarm chain is an ordered list of content that are linked as a forkless chain. . This is simply modeled as linked manifests.

a channel is a sequence of manifests (S) and a relative path P with a starting manifest M and a streamsize n (can be infinite). A channel is well-formed or regular if in every manifest in the stream P resolves to a consistent mime type T . For instance , if T is application/bzz-manifest+json, we say the channel is a manifest channel, if the mime-type is mpeg, its a video channel.

A primary channel is a channel that actually respect chronological order of creation.

A live channel is a primary channel that keeps updating (adding episodes to the end of the chain) can have a (semi)-persistent mime-type for path P

A blockstream channel is a primary channel provable linked in time via hashes.

A signed channel is a primary channel provably linked by signatures (sequence position index signed by the publisher)

Trackers are a manifest channel which tracks updates to a primary channel and provides forward linking .

Example channels:

• name histories, e.g updates of a domain, temporal snapshots of content
• blockchain: blockchain is a special case of blockstream
• git graph, versioning
• modeling a source of information: provable communication with hash chain, not allowed to fork, numbered.

content trackers

reverse index of a stream

• contains next links to following state
• published after next state
• publish provable quality metrics:
• age: starting date of tracker vs date of orig content
• neg exp forgetting(track date vs primary date of next episode) ~ alertness, puncuality (tracker
• git version control

every named host defines a timeline,

• create a manifest stream tracking a site

Ways to link manifests

examples

{ "entries":
  [
    {
      "host": "fefe.eth",
      "number": 9067,
      "previous": "ffca34987",
      "next": "aefbc4569ab",
      "this": "90daefaaabbc",
    }
  ],
  "auth": "3628aeefbc7689523aebc2489",
}

Name resolution

The host part in a bzz webaddress should be resolved with our version of DNS, ie. using both NameReg (name registration contract on ethereum) and a simple mutable storage in swarm.

signed version store

The point of channels (https://github.com/ethereum/go-ethereum/wiki/Swarm---Channels ) is to have a total order over a set of manifests.

The typical usecase is that it should be enough to know the name of a site or document to always see the latest version of a software or get the current episode of your favourite series or the consensus state of a blockchain. It should also be possible to deterministically derive the key to future content...

One possibility is to modify the NameReg entry in the blockchain to point to a swarm hash. Recording each change on the blockchain results in an implicit live channel linking. This scheme is simple inasmuch as it puts authentication completely on the chain. However, it is expensive and not viable given the number of publishers and typical rate of update.

Alternatively, swarm provides the protocol for associating a channel and a position with a swarm hash. The versioning can be authenticated since a message containing host name, sequence position index and swarm hash is signed by the public key registered in ethereum NameReg for the host.

Publishers, fans or paid bookkeepers track updates of a channel and wrap accumulated messages into a tracker manifest. Most probably publishers would broadcast updates of a channel manifest in the first place.

This special key-value store can be implemented as a mutable store: the value with a higher index will simply override the previous one.

There can be various standards to derive lookup key deterministically the simplest one is HASH(host:version) for a specific version and HASH(host) for the latest version. The content has the following structure:

sign[<host>, <version>, <timestamp>, <hash>]

Retrieve request for a signed version is the same as a request for a hash.

[RetrieveMsg, HASH(host:version), id, timeout, MUTABLE] 
[RetrieveMsg, HASH(host:0), id, timeout, MUTABLE] 

Store request for a signed version is the same as for a hash:

[StoreMsg, key, id, MUTABLE, Sign[host, version, time.Unix(), hash]] 

Format

It is up to debate how we distinguish names to be resolved.

An early idea was to use a top level domain, such as .eth ( == <host>.eth) this might limit the possibilities

Another idea was to have it as or part of the protocol: eth://my-website.home or eth+bzz://my-website.home. This are semantically incorrect, however.

Third, put an eth inside the host somehow.

Ad-hoc constructs like bzz://eth:my-website.home will be rejected by host pattern matchers.

Abusing subdomains bzz://eth.my-website.home would cause ambiguity and potential collision. Abusing auth user:pass@my-website.home would disable basic auth.

A suggestion that most aligns with the signed versioning and very simple is that we look up everything that is not a 32 byte hash format for a public key. The version of the site is looked up using the port part of the host. A specific version is given after the :.

The generic pattern then:

   (<version_chain>.)<host>(:<number>)(/<path>)

example 0

  bzz://breaking.bad.tv/s4/e2/video

• breaking.bad.tv is looked up in NameReg to yield public key P
• breaking.bad.tv is looked up in the immutable store to yield a message [_breaking.bad.tv_,0,3,aebf45fbf6ae6aaaafedcbcb467]
• aebf45fbf6ae6aaaafedcbcb467 is looked up in swarm to yield the manifest
• manifest entry for path /s4/e2/video results in the actual document's root key

example 1

  bzz://breaking.bad.tv/video

resolves the following way:

• breaking.bad.tv is looked up in NameReg to yield public key P
• breaking.bad.tv is looked up in the immutable store to yield - by H(cookie) - a message [_breaking.bad.tv_,s5:e12,3,aebf45fbf6ae6aaaafedcbcb467] signed by P
• aebf45fbf6ae6aaaafedcbcb467 is looked up in swarm to yield the manifest
• manifest entry for path video results in the actual document's root key

example 2

  bzz://current.breaking.bad.tv:s4:e10/video

• breaking.bad.tv is looked up in NameReg to yield public key P
• current.breaking.bad.tv:s4:e10 is looked up in the immutable store to yield a message [current.breaking.bad.tv,s4:e10,3,45fbf6ae6aaaafedcbcb467ccc]
• 45fbf6ae6aaaafedcbcb467ccc is looked up in swarm to yield the manifest
• manifest entry for path video results in the actual document's root key

example 3

  bzz://breaking.bad.tv/playlist

• same as ex 2...
• manifest entry for path playlist results in a playlist manifest

example 4

  bzz://stable.ethereum.org:8.1/download/go/mac-os

• stable.ethereum.org is looked up in NameReg to yield public key P
• stable.ethereum.org:s4:e10 is looked up in the immutable store to yield a message [stable.ethereum.org,s4:e10,3,45fbf6ae6aaaafedcbcb467ccc]
• 45fbf6ae6aaaafedcbcb467ccc is looked up in swarm to yield the manifest
• manifest entry for path video results in the actual document's root key

Generalised content streaming, subscriptions.