feat(concord): add rekey distribution (CORD-06)

Non-ratcheted async key rotation to remove members from a channel or (root scope) the whole community, pinned to Concord v2 (Armada rekey.ts): - RekeyPayload: the 72-byte scope_id||epoch_be8||new_key blob codec - RekeyBlob: per-recipient {locator, wrapped} entry - ConcordRekey: blobFor (locator = recipient pseudonym; wrapped = base64 payload NIP-44-encrypted under the rotator<->recipient pairwise key), kind-3303 rumor tags (scope/newepoch/prevepoch/prevcommit/chunk) and content codec, and findNewKey (recipient computes their locator, matches, decrypts, verifies scope+epoch) with absence == removal Test proves remaining members recover the rotated key while a removed member finds no matching blob, and that the locator is epoch-bound. Green on :quartz:jvmTest. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01CzJ2Cwo8tg4oZq43oRa3ig
2026-08-12 09:13:23 +00:00 · 2026-07-09 22:20:51 +00:00
parent 06fa80da65
commit b0e3594eaa
3 changed files with 292 additions and 0 deletions
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+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.quartz.concord.cord06Rekey
+
+import com.vitorpamplona.quartz.nip01Core.core.toHexKey
+import com.vitorpamplona.quartz.nip01Core.crypto.KeyPair
+import kotlin.test.Test
+import kotlin.test.assertContentEquals
+import kotlin.test.assertEquals
+import kotlin.test.assertNull
+
+class ConcordRekeyTest {
+    private val rotator = KeyPair()
+    private val alice = KeyPair()
+    private val bob = KeyPair()
+    private val carol = KeyPair() // removed member
+
+    private val scope = ByteArray(32) { 0x42 }
+    private val newEpoch = 1L
+    private val newKey = ByteArray(32) { 0x7E }
+
+    private fun blobFor(recipient: KeyPair) = ConcordRekey.blobFor(rotator.privKey!!, rotator.pubKey, recipient.pubKey, scope, newEpoch, newKey)
+
+    private fun find(
+        recipient: KeyPair,
+        blobs: List<RekeyBlob>,
+        epoch: Long = newEpoch,
+    ) = ConcordRekey.findNewKey(blobs, recipient.privKey!!, recipient.pubKey, rotator.pubKey, scope, epoch)
+
+    @Test
+    fun payloadEncodesAndDecodes() {
+        val decoded = RekeyPayload.decode(RekeyPayload(scope, 42, newKey).encode())
+        assertContentEquals(scope, decoded?.scopeId)
+        assertEquals(42L, decoded?.epoch)
+        assertContentEquals(newKey, decoded?.newKey)
+        assertNull(RekeyPayload.decode(ByteArray(70))) // wrong size
+    }
+
+    @Test
+    fun remainingMembersGetTheKeyAndRemovedMembersDoNot() {
+        // Rotator distributes the new key to Alice and Bob, but not Carol.
+        val blobs = listOf(blobFor(alice), blobFor(bob))
+        val content = ConcordRekey.encodeContent(blobs)
+        val roundTripped = ConcordRekey.decodeContent(content)
+
+        assertContentEquals(newKey, find(alice, roundTripped))
+        assertContentEquals(newKey, find(bob, roundTripped))
+        assertNull(find(carol, roundTripped)) // no blob for Carol ⇒ removed
+    }
+
+    @Test
+    fun wrongEpochDoesNotMatch() {
+        val blobs = listOf(blobFor(alice))
+        assertNull(find(alice, blobs, epoch = 2L)) // locator is epoch-bound
+    }
+
+    @Test
+    fun tagsCarryScopeEpochAndChunk() {
+        val tags = ConcordRekey.tags(scope, newEpoch, prevEpoch = 0, prevCommit = "ab".repeat(32), chunkIndex = 1, chunkTotal = 3)
+        assertEquals(scope.toHexKey(), tags.first { it[0] == ConcordRekey.TAG_SCOPE }[1])
+        assertEquals("1", tags.first { it[0] == ConcordRekey.TAG_NEWEPOCH }[1])
+        val chunk = tags.first { it[0] == ConcordRekey.TAG_CHUNK }
+        assertEquals("1", chunk[1])
+        assertEquals("3", chunk[2])
+    }
+}