Groups: leave notices, member removal, rekey, admin handoff (signed update chain, key epochs)

README.md

@@ -64,8 +64,11 @@ confirmation closes that invite. The inviter
 should stay online briefly so existing members can learn about newly joined
 devices through one-hop introductions. Use `entangle group list`,
 `entangle group members <name>`, and `entangle group leave <name>` to inspect
-or leave groups. A second Entangle server using the same data directory gets
-a temporary ID while the first server is running. See
+or leave groups. Human admins can run `entangle group remove <group> <member>`
+to remove a member and rotate the key, `entangle group rekey <group>` to
+rotate without changing membership, and `entangle group admin <group> <member>`
+to hand off administration. A second Entangle server using the same data
+directory gets a temporary ID while the first server is running. See
 [docs/SETUP.md](docs/SETUP.md) for group setup, firewall, client configuration,
 and a two-machine smoke test.
 
@@ -82,8 +85,9 @@ The standalone commands are `entangle serve` (default), `entangle node`, and
 ## Design and security
 
 The crate boundaries, message flow, wire format, and security limitations are
-documented in [docs/ARCHITECTURE.md](docs/ARCHITECTURE.md). Protocol version 4
-uses group-bound Noise links; all devices must share a group to communicate.
+documented in [docs/ARCHITECTURE.md](docs/ARCHITECTURE.md). Protocol version 5
+uses epoch-bound, group-authenticated Noise links with signed membership
+updates; all devices must share a group to communicate.
 
 ## License
 

crates/entangle-core/src/lib.rs

@@ -7,7 +7,7 @@ use std::{fmt, path::Path};
 pub mod sas;
 
 /// Current version of the Entangle control protocol.
-pub const PROTOCOL_VERSION: u32 = 4;
+pub const PROTOCOL_VERSION: u32 = 5;
 
 /// A process-unique particle identity rendered as 32 lowercase hexadecimal digits.
 #[derive(Clone, Eq, Hash, Ord, PartialEq, PartialOrd, Serialize)]
@@ -20,10 +20,42 @@ pub struct Member {
     pub particle_id: String,
     pub name: String,
     pub static_key: String,
+    pub sign_key: String,
     pub added_by: String,
     pub added_at: String,
 }
 
+/// A signed group membership and key update.
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
+pub struct GroupUpdate {
+    pub group_id: String,
+    pub epoch: u32,
+    pub key_hex: String,
+    pub admin: String,
+    pub admin_sign_key: String,
+    pub revoked: Vec<Revocation>,
+    pub kind: UpdateKind,
+    pub issued_by: String,
+    pub issued_at: String,
+    pub signature: String,
+}
+
+/// A member removed from a group, bound to the static key that was revoked.
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
+pub struct Revocation {
+    pub particle_id: String,
+    pub static_key: String,
+}
+
+/// The operation represented by a signed group update.
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
+#[serde(tag = "type", rename_all = "snake_case")]
+pub enum UpdateKind {
+    Remove { particle_id: String },
+    Rekey,
+    AdminHandoff { to: String },
+}
+
 impl ParticleId {
     /// Creates a fresh identity using the OS random number generator; callers may persist it.
     pub fn generate() -> Self {