use Add+Remove instead of Update

decentralised.org

@@ -95,8 +95,9 @@ application's group membership:
   ~Remove~ proposal is added to remove them from the MLS group.
 - for any user who is in both the MLS group and in the application's group,
   check if any extremity has a ~KeyPackage~ for that user with a higher
-  generation number, and if so, an ~Update~ proposal is added with the user's
-  ~KeyPackage~ with the highest generation number.
+  generation number, and if so, a ~Remove~ proposal is added with the user's
+  leaf number, and an ~Add~ proposal is added with the user's ~KeyPackage~ with
+  the highest generation number.
 - for any user who is not in the MLS group, but is in the application's group,
   an ~Add~ proposal is added.  If the user is present in any of the
   extremities, then the ~KeyPackage~ with the highest generation number is
@@ -130,6 +131,8 @@ When another user receives a ~Commit~, they should
   Carol's random number generator is good, then this may not be much of a
   problem.  Bob will also notice this, and can make a new Update to re-add
   entropy from his RNG (as long as his Update isn't discarded again).
+- we will blank a bunch of nodes, which means that we may have decreased
+  performance.
 
 * Todo
 

src/group.ts

@@ -33,7 +33,7 @@ import {
     MLSCiphertext,
     Add,
     Commit,
-    Update,
+    Remove,
     ProposalWrapper,
     Sender,
     UpdatePath,
@@ -417,7 +417,7 @@ export class Group {
         return this.extremities.size > 1;
     }
 
-    prepareCommit(): [Epoch, Uint8Array, Update[], [Epoch, Uint8Array][], boolean, Uint8ArrayMap<number>, Uint8ArrayMap<KeyPackage>] {
+    prepareCommit(): [Epoch, Uint8Array, (Add|Remove)[], [Epoch, Uint8Array][], boolean, Uint8ArrayMap<number>, Uint8ArrayMap<KeyPackage>] {
         let baseEpoch: Epoch = -1;
         let baseSender: Uint8Array;
 
@@ -495,7 +495,7 @@ export class Group {
         }
 
         // construct update proposals
-        const updates: Update[] = [];
+        const updates: (Add|Remove)[] = [];
         for (const [, epochStr, leafNum] of maxGenerations.values()) {
             if (epochStr === undefined) {
                 continue;
@@ -504,7 +504,8 @@ export class Group {
             if (eqUint8Array(identity, keyPackage.credential.identity)) {
                 updatePathRequired = true;
             } else {
-                updates.push(new Update(keyPackage));
+                updates.push(new Remove(leafNum));
+                updates.push(new Add(keyPackage));
             }
         }
 

test/group.test.ts

@@ -131,7 +131,7 @@ describe("Group", () => {
             groupA.prepareCommit();
 
         expect(updates1).toEqual([]);
-        expect(resolves1).toEqual([])
+        expect(resolves1).toEqual([]);
 
         const [, mlsPlaintext1, , ] = await groupA.commit(
             [new ProposalWrapper(new Remove(3))],
@@ -167,7 +167,7 @@ describe("Group", () => {
             groupB.prepareCommit();
 
         expect(updates2).toEqual([]);
-        expect(resolves2).toEqual([])
+        expect(resolves2).toEqual([]);
 
         const [, mlsPlaintext2, welcome2, ] = await groupB.commit(
             [
@@ -240,7 +240,7 @@ describe("Group", () => {
             groupA.prepareCommit();
 
         expect(updates1).toEqual([]);
-        expect(resolves1).toEqual([])
+        expect(resolves1).toEqual([]);
 
         const [mlsCiphertext1, , , ] = await groupA.commit(
             [new ProposalWrapper(new Remove(3))],
@@ -347,7 +347,7 @@ describe("Group", () => {
             groupA.prepareCommit();
 
         expect(updates1A).toEqual([]);
-        expect(resolves1A).toEqual([])
+        expect(resolves1A).toEqual([]);
 
         const [, mlsPlaintext1A, , ] = await groupA.commit(
             [],
@@ -361,7 +361,7 @@ describe("Group", () => {
             groupB.prepareCommit();
 
         expect(updates1B).toEqual([]);
-        expect(resolves1B).toEqual([])
+        expect(resolves1B).toEqual([]);
 
         const [, mlsPlaintext1B, , ] = await groupB.commit(
             [],
@@ -375,7 +375,7 @@ describe("Group", () => {
             groupC.prepareCommit();
 
         expect(updates1C).toEqual([]);
-        expect(resolves1C).toEqual([])
+        expect(resolves1C).toEqual([]);
 
         const [, mlsPlaintext1C, , ] = await groupC.commit(
             [],
@@ -389,7 +389,7 @@ describe("Group", () => {
             groupD.prepareCommit();
 
         expect(updates1D).toEqual([]);
-        expect(resolves1D).toEqual([])
+        expect(resolves1D).toEqual([]);
 
         const [, mlsPlaintext1D, , ] = await groupD.commit(
             [],
@@ -430,8 +430,8 @@ describe("Group", () => {
         const [baseEpoch2, baseSender2, updates2, resolves2, updatePathRequired2, ,] =
             groupE.prepareCommit();
 
-        expect(updates2.length).toEqual(3);
-        expect(resolves2.length).toEqual(3)
+        expect(updates2.length).toEqual(6);
+        expect(resolves2.length).toEqual(3);
 
         const [, mlsPlaintext2, , ] = await groupE.commit(
             [],