private-group-spec

Private-Groups Spec (v1)

A specification for implementing private groups in scuttlebutt.

The fundamentals of this spec are:

1. uses envelope for encryption of content
2. has group_ids which are safe to share publicly
3. adding people to the group is done with group's knowledge
4. supports disclosing of message content
   • but this leaks info about the group (peak at other messages / authors)

envelope encryption in scuttlebutt

In adition to the envelope-spec, there are some scuttlebutt-specific specifications

See spec here

recipient key derivation

box1 took feedIds from the content.recps field and directly used these for encryption.

In envelope, we instead take "ids" from content.recps, and map each to a pair{ key, key_type } where":

• key is the shared key which we're going to a key_slot, and
• key_type is the "key management schema" which that key is employing

Type of id	How key is found	scheme
private group id	a key-store	"envelope-large-symmetric-group"
classic feedId	diff-hellman styles	"envelope-id-based-dm-converted-ed25519"
published private key	TODO	"envelope-signed-dh-key-curve25519" ??

see key-schemes.json for the canonical list of accepted

group management

A minimal amount of agreement to make coordination easier:

• creating a new group
• adding someone to your group

---

TODO

describe

• how all these things might be woven together
• where state is tracked off-chain (in a key-store)

scuttlebutt private-groups spec (v2)

Could modify this spec:

1. • same
2. • same
3. • same
4. supports privacy fiendly disclosing of message content
   • all internal cypherlinks are "cloaked"