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copy from https://scuttlebot.io/more/protocols/secure-scuttlebutt.html

Michael Williams committed on 11/3/2016, 12:21:12 PM
Parent: f2ddbc9bb74bc33eda174f962215eefeb8dae202

Files changed

SUMMARY.mdchanged
assets/gossip-graph1.pngadded
assets/gossip-graph2.pngadded
concepts/blob.mdadded
concepts/feed.mdadded
concepts/gossip.mdadded
concepts/identity.mdadded
concepts/link.mdadded
concepts/local.mdadded
concepts/message.mdadded
concepts/private-message.mdadded
concepts/pub.mdadded
SUMMARY.mdView
@@ -1,8 +1,14 @@
11 …
22 … * ![](assets/hermes.png)
33 … * [Introduction](README.md)
44 … * [Concepts](concepts/index.md)
5- - [Append only logs](concepts/append-only-log.md)
6- - [Content addressable storage](concepts/content-addressable-storage.md)
7- - [Key pairs](concepts/key-pairs.md)
5 …+ - [Identity](concepts/identity.md)
6 …+ - [Feed](concepts/feed.md)
7 …+ - [Message](concepts/message.md)
8 …+ - [Private Message](concepts/private-message.md)
9 …+ - [Link](concepts/link.md)
10 …+ - [Gossip](concepts/gossip.md)
11 …+ - [Local](concepts/local.md)
12 …+ - [Pub](concepts/pub.md)
13 …+ - [Blob](concepts/blob.md)
814 … 
assets/gossip-graph1.png
assets/gossip-graph1.png
assets/gossip-graph2.png
assets/gossip-graph2.png
concepts/blob.mdView
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1 …+# Blob
2 …+
3 …+
concepts/feed.mdView
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1 …+# Feed
2 …+
3 …+A feed is a signed append-only sequence of messages. Each identity has exactly one feed.
4 …+
5 …+Note that append-only means you cannot delete an existing message, or change your history. This is enforced by a per-feed blockchain. This is to ensure the entire network converges on the same state.
concepts/gossip.mdView
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1 …+# Gossip
2 …+
3 …+## Following
4 …+
5 …+Users choose which feeds to synchronize by following them. Presently, Scuttlebot's replicate plugin, which is enabled by default, looks on the master user's feed for `type: contact` messages to know which users are currently followed.
6 …+
7 …+## Replication
8 …+
9 …+Since feeds are append-only, replication is simple: request all messages in the feed that are newer than the latest message you know about. Scuttlebot maintains a table of known peers, which it cycles through, asking for updates for all followed feeds.
10 …+
11 …+Since feeds are append-only, gossip is simple: request all messages in the feed that are newer than the latest message you know about. Scuttlebot maintains a table of known peers, which it cycles through, asking for updates for all followed feeds.
12 …+
13 …+## Network
14 …+
15 …+The protocol creates a [global gossip network](https://en.wikipedia.org/wiki/Gossip_protocol). This means that information is able to distribute across multiple machines, without requiring direct connections between them.
16 …+
17 …+![Gossip graph 1](../assets/gossip-graph1.png)
18 …+
19 …+Even though Alice and Dan lack a direct connection, they can still exchange feeds:
20 …+
21 …+![Gossip graph 2](../assets/gossip-graph2.png)
22 …+
23 …+This is because gossip creates "transitive" connections between computers. Dan's messages travel through Carla and the Pub to reach Alice, and visa-versa.
concepts/identity.mdView
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1 …+# Identity
2 …+
3 …+An identity is simply a [ed25519 key pair](http://ed25519.cr.yp.to/). The public key is used as the identifier.
4 …+
5 …+There is no worldwide store of identities. Users must exchange pubkeys, either by publishing them on their feeds, or out-of-band.
concepts/link.mdView
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1 …+# Link
2 …+
3 …+Messages can reference three types of Secure Scuttlebutt entities: messages, feeds, and blobs (i.e. files). Messages and blobs are referred to by their hashes, but a feed is referred to by its signing public key.
4 …+
5 …+To indicate the type of ID, a "sigil" is prepended to the string. They are:
6 …+
7 …+- `@` for feeds
8 …+- `%` for messages
9 …+- `&` for blobs
10 …+
11 …+Additionally, each ID has a "tag" appended to indicate the hash or key algorithm. Some example IDs:
12 …+
13 …+- A feed: `@LA9HYf5rnUJFHHTklKXLLRyrEytayjbFZRo76Aj/qKs=.ed25519`
14 …+- A message: `%MPB9vxHO0pvi2ve2wh6Do05ZrV7P6ZjUQ+IEYnzLfTs=.sha256`
15 …+- A blob: `&Pe5kTo/V/w4MToasp1IuyMrMcCkQwDOdyzbyD5fy4ac=.sha256`
16 …+
17 …+When IDs are found in the messages, they may be treated as links, with the keyname acting as a "relation" type. An example of this:
18 …+
19 …+```shell
20 …+sbot publish --type post \
21 …+ --root "%MPB9vxHO0pvi2ve2wh6Do05ZrV7P6ZjUQ+IEYnzLfTs=.sha256" \
22 …+ --branch "%kRi8MzGDWw2iKNmZak5STshtzJ1D8G/sAj8pa4bVXLI=.sha256" \
23 …+ --text "this is a reply!"
24 …+```
25 …+
26 …+```javascript
27 …+sbot.publish({
28 …+ type: "post",
29 …+ root: "%MPB9vxHO0pvi2ve2wh6Do05ZrV7P6ZjUQ+IEYnzLfTs=.sha256",
30 …+ branch: "%kRi8MzGDWw2iKNmZak5STshtzJ1D8G/sAj8pa4bVXLI=.sha256",
31 …+ text: "this is a reply!"
32 …+})
33 …+```
34 …+
35 …+In this example, the root and branch keys are the relations. SSB automatically builds an index based on these links, to allow queries such as "all messages with a root link to this message."
concepts/local.mdView
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1 …+# local
2 …+
3 …+SSB is hostless: each computer installs the same copy of software and has equal rights in the network. Devices discover each other over the LAN with multicast UDP and sync automatically.
concepts/message.mdView
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1 …+# Message
2 …+
3 …+Each message contains:
4 …+
5 …+A signature
6 …+The signing public key
7 …+A content-hash of the previous message
8 …+A sequence number
9 …+A timestamp
10 …+An identifier of the hashing algorithm in use (currently only "sha256" is supported)
11 …+A content object
12 …+Here's an example message:
13 …+
14 …+```
15 …+{
16 …+ "previous": "%26AC+gU0t74jRGVeDY013cVghlZRc0nfUAnMnutGGHM=.sha256",
17 …+ "author": "@hxGxqPrplLjRG2vtjQL87abX4QKqeLgCwQpS730nNwE=.ed25519",
18 …+ "sequence": 216,
19 …+ "timestamp": 1442590513298,
20 …+ "hash": "sha256",
21 …+ "content": {
22 …+ "type": "vote",
23 …+ "vote": {
24 …+ "link": "%WbQ4dq0m/zu5jxll9zUbe0iGmDOajCx1ZkLKjZ80JvI=.sha256",
25 …+ "value": 1
26 …+ }
27 …+ },
28 …+ "signature": "Sjq1C3yiKdmi1TWvNqxIk1ZQBf4pPJYl0HHRDVf/xjm5tWJHBaW4kXo6mHPcUMbJYUtc03IvPwVqB+BMnBgmAQ==.sig.ed25519"
29 …+}
30 …+```
concepts/private-message.mdView
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1 …+# Private Message
2 …+
3 …+For private sharing, Scuttlebot uses [libsodium](http://doc.libsodium.org/) to encrypt confidential log-entries. Feed IDs are public keys, and so once two feeds are mutually following each other, they can exchange confidential data freely.
4 …+
5 …+Private-box is a format for encrypting a private message to many parties. It is designed according to the [audit-driven crypto design process](https://github.com/crypto-browserify/crypto-browserify/issues/128). You can find the repository on at [github:dominictarr/private-box](https://github.com/auditdrivencrypto/private-box)
concepts/pub.mdView
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1 …+# Pub
2 …+
3 …+To sync across the Internet, "Pub" nodes run at public IPs and follow users. They are essentially mail-bots which improve uptime and availability. Users generate invite-codes to command Pubs to follow their friends. The Scuttlebot community runs some Pubs, and anybody can create and introduce their own.

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