Extend signing-key pin to persisted identity so it survives restart/eviction

The TOFU signing-key pin lived only in the in-memory peerRegistry. When
a previously seen peer was no longer in the registry (app restart, or
reconcileConnectivity pruning an offline peer), the announce trust check
saw no pinned key, treated the announce as first contact, and
persistIdentity overwrote the cached signing key/nickname — so an
attacker could replay a victim's noiseKey/peerID with their own signing
key and bypass the spoofing protection for returning/offline peers.

Fixes:

- BLEAnnounceHandler now falls back to the persisted cryptographic
  identity (via a new persistedSigningPublicKey environment closure)
  when the registry has no signing key for the peer, so the pin remains
  effective across registry eviction and app restarts. BLEService wires
  it to SecureIdentityStateManager.getCryptoIdentitiesByPeerIDPrefix,
  the same synchronous identity-manager read already used on the packet
  path by signedSenderDisplayName.
- SecureIdentityStateManager.upsertCryptographicIdentity refuses to
  replace a persisted signing key with a different one (security-logged,
  nickname update included in the refusal), mirroring the registry
  policy. First-writer-wins persistence also removes any race where a
  concurrent announce could poison the stored identity.
- CryptographicIdentity entries (incl. the signing-key pin) are now part
  of the encrypted IdentityCache, so they actually persist across app
  restarts; previously they were in-memory only. Old caches without the
  new field still decode (decodeIfPresent), and clearAllIdentityData /
  panic wipe clears the pins as before.

Legitimate re-keying: presenting a different signing key for the same
noise key is exactly the attack being blocked, so refusal is correct
and permanent until the peer adopts a new noise identity (new peerID)
or the user explicitly clears identity data. Repeated rejected announces
follow the existing unverified-announce path (log + ignore); no retry
loops or crashes.

Tests: handler-level persisted-pin mismatch/match/precedence cases, an
end-to-end restart+eviction test with real Ed25519 keys and a real
SecureIdentityStateManager showing the attacker replay is rejected and
the persisted identity is untouched while the victim re-announce is
accepted, and identity-manager tests for the pinned-key refusal and the
keychain round-trip of the pin.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

bitchat/Identity/IdentityModels.swift

@@ -141,22 +141,44 @@ enum TrustLevel: String, Codable {
 struct IdentityCache: Codable {
     // Fingerprint -> Social mapping
     var socialIdentities: [String: SocialIdentity] = [:]
-    
+
     // Nickname -> [Fingerprints] reverse index
     // Multiple fingerprints can claim same nickname
     var nicknameIndex: [String: Set<String>] = [:]
-    
+
     // Verified fingerprints (cryptographic proof)
     var verifiedFingerprints: Set<String> = []
-    
+
     // Last interaction timestamps (privacy: optional)
-    var lastInteractions: [String: Date] = [:] 
-    
+    var lastInteractions: [String: Date] = [:]
+
     // Blocked Nostr pubkeys (lowercased hex) for geohash chats
     var blockedNostrPubkeys: Set<String> = []
-    
+
+    // Fingerprint -> Cryptographic identity (noise + pinned signing key).
+    // Persisting the signing-key pin is security-critical: it must survive
+    // app restarts so an attacker cannot replay a known peer's
+    // noiseKey/peerID with their own signing key and be treated as first
+    // contact (TOFU downgrade).
+    var cryptographicIdentities: [String: CryptographicIdentity] = [:]
+
     // Schema version for future migrations
     var version: Int = 1
+
+    init() {}
+
+    // Custom decoding so caches written by older builds (without
+    // `cryptographicIdentities`) still load instead of being discarded.
+    init(from decoder: Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        socialIdentities = try container.decodeIfPresent([String: SocialIdentity].self, forKey: .socialIdentities) ?? [:]
+        nicknameIndex = try container.decodeIfPresent([String: Set<String>].self, forKey: .nicknameIndex) ?? [:]
+        verifiedFingerprints = try container.decodeIfPresent(Set<String>.self, forKey: .verifiedFingerprints) ?? []
+        lastInteractions = try container.decodeIfPresent([String: Date].self, forKey: .lastInteractions) ?? [:]
+        blockedNostrPubkeys = try container.decodeIfPresent(Set<String>.self, forKey: .blockedNostrPubkeys) ?? []
+        cryptographicIdentities = try container.decodeIfPresent([String: CryptographicIdentity].self, forKey: .cryptographicIdentities) ?? [:]
+        version = try container.decodeIfPresent(Int.self, forKey: .version) ?? 1
+    }
 }
 
 //

bitchat/Identity/SecureIdentityStateManager.swift

@@ -145,7 +145,8 @@ final class SecureIdentityStateManager: SecureIdentityStateManagerProtocol {
     
     // In-memory state
     private var ephemeralSessions: [PeerID: EphemeralIdentity] = [:]
-    private var cryptographicIdentities: [String: CryptographicIdentity] = [:]
+    // Cryptographic identities (including pinned signing keys) live inside
+    // `cache` so they persist across app restarts; see IdentityCache.
     private var cache: IdentityCache = IdentityCache()
     
     // Thread safety
@@ -296,6 +297,15 @@ final class SecureIdentityStateManager: SecureIdentityStateManagerProtocol {
     // MARK: - Cryptographic Identities
 
     /// Insert or update a cryptographic identity and optionally persist its signing key and claimed nickname.
+    ///
+    /// TOFU signing-key pinning: once a signing key has been persisted for a
+    /// fingerprint, an update carrying a *different* signing key is refused in
+    /// full (including the claimed-nickname update) and security-logged. This
+    /// mirrors `BLEPeerRegistry.upsertVerifiedAnnounce` — without it, an
+    /// attacker replaying a victim's noiseKey/peerID with their own signing
+    /// key could overwrite the victim's persisted identity while the victim is
+    /// offline or after an app restart. Recovering from a legitimate signing
+    /// re-key requires a new noise identity or explicit user re-verification.
     /// - Parameters:
     ///   - fingerprint: SHA-256 hex of the Noise static public key
     ///   - noisePublicKey: Noise static public key data
@@ -304,7 +314,13 @@ final class SecureIdentityStateManager: SecureIdentityStateManagerProtocol {
     func upsertCryptographicIdentity(fingerprint: String, noisePublicKey: Data, signingPublicKey: Data?, claimedNickname: String? = nil) {
         queue.async(flags: .barrier) {
             let now = Date()
-            if var existing = self.cryptographicIdentities[fingerprint] {
+            if var existing = self.cache.cryptographicIdentities[fingerprint] {
+                if let pinnedSigningKey = existing.signingPublicKey,
+                   let announcedSigningKey = signingPublicKey,
+                   pinnedSigningKey != announcedSigningKey {
+                    SecureLogger.warning("🚨 Refusing to replace pinned signing key for \(fingerprint.prefix(8))… (possible impersonation attempt)", category: .security)
+                    return
+                }
                 // Update keys if changed
                 if existing.publicKey != noisePublicKey {
                     existing = CryptographicIdentity(
@@ -314,7 +330,7 @@ final class SecureIdentityStateManager: SecureIdentityStateManagerProtocol {
                         firstSeen: existing.firstSeen,
                         lastHandshake: now
                     )
-                    self.cryptographicIdentities[fingerprint] = existing
+                    self.cache.cryptographicIdentities[fingerprint] = existing
                 } else {
                     // Update signing key and lastHandshake
                     existing.signingPublicKey = signingPublicKey ?? existing.signingPublicKey
@@ -325,7 +341,7 @@ final class SecureIdentityStateManager: SecureIdentityStateManagerProtocol {
                         firstSeen: existing.firstSeen,
                         lastHandshake: now
                     )
-                    self.cryptographicIdentities[fingerprint] = updated
+                    self.cache.cryptographicIdentities[fingerprint] = updated
                 }
                 // Persist updated state (already assigned in branches above)
             } else {
@@ -337,7 +353,7 @@ final class SecureIdentityStateManager: SecureIdentityStateManagerProtocol {
                     firstSeen: now,
                     lastHandshake: now
                 )
-                self.cryptographicIdentities[fingerprint] = entry
+                self.cache.cryptographicIdentities[fingerprint] = entry
             }
 
             // Optionally persist claimed nickname into social identity
@@ -369,7 +385,7 @@ final class SecureIdentityStateManager: SecureIdentityStateManagerProtocol {
         queue.sync {
             // Defensive: ensure hex and correct length
             guard peerID.isShort else { return [] }
-            return cryptographicIdentities.values.filter { $0.fingerprint.hasPrefix(peerID.id) }
+            return cache.cryptographicIdentities.values.filter { $0.fingerprint.hasPrefix(peerID.id) }
         }
     }
     
@@ -528,8 +544,7 @@ final class SecureIdentityStateManager: SecureIdentityStateManagerProtocol {
         queue.async(flags: .barrier) {
             self.cache = IdentityCache()
             self.ephemeralSessions.removeAll()
-            self.cryptographicIdentities.removeAll()
-            
+
             // Delete from keychain
             let deleted = self.keychain.deleteIdentityKey(forKey: self.cacheKey)
             SecureLogger.logKeyOperation(.delete, keyType: "identity cache", success: deleted)

bitchat/Services/BLE/BLEAnnounceHandler.swift

@@ -17,6 +17,11 @@ struct BLEAnnounceHandlerEnvironment {
     /// Noise and signing public keys already recorded for the peer, if any
     /// (single registry read so both come from one consistent snapshot).
     let existingPeerKeys: (PeerID) -> (noisePublicKey: Data?, signingPublicKey: Data?)
+    /// Signing key from the persisted cryptographic identity for the peer, if
+    /// any. Registry pins do not survive app restarts or offline-peer
+    /// eviction; this fallback keeps the TOFU signing-key pin effective for
+    /// returning peers.
+    let persistedSigningPublicKey: (PeerID) -> Data?
     /// Verifies the packet signature against the announced signing key.
     let verifySignature: (_ packet: BitchatPacket, _ signingPublicKey: Data) -> Bool
     /// Direct link state for the peer (BLE-queue read).
@@ -102,7 +107,16 @@ final class BLEAnnounceHandler {
         // Suppress announce logs to reduce noise
 
         // Precompute signature verification outside barrier to reduce contention
-        let existingPeerKeys = env.existingPeerKeys(peerID)
+        var existingPeerKeys = env.existingPeerKeys(peerID)
+        if existingPeerKeys.signingPublicKey == nil {
+            // The registry entry (and its signing-key pin) is dropped on app
+            // restart and offline-peer eviction, but the persisted
+            // cryptographic identity survives both. Fall back to it so a
+            // returning peer is not treated as first contact — otherwise an
+            // attacker could replay the peer's noiseKey/peerID with their own
+            // signing key and re-pin the identity (TOFU downgrade).
+            existingPeerKeys.signingPublicKey = env.persistedSigningPublicKey(peerID)
+        }
         let hasSignature = packet.signature != nil
         let signatureValid: Bool
         if hasSignature {

bitchat/Services/BLE/BLEService.swift

@@ -3035,6 +3035,15 @@ extension BLEService {
                     return (info?.noisePublicKey, info?.signingPublicKey)
                 }
             },
+            persistedSigningPublicKey: { [weak self] peerID in
+                // Same synchronous identity-manager read pattern as
+                // signedSenderDisplayName(for:from:); the manager serializes
+                // access on its own internal queue.
+                guard let self = self else { return nil }
+                return self.identityManager.getCryptoIdentitiesByPeerIDPrefix(peerID)
+                    .compactMap { $0.signingPublicKey }
+                    .first
+            },
             verifySignature: { [weak self] packet, signingPublicKey in
                 self?.noiseService.verifyPacketSignature(packet, publicKey: signingPublicKey) ?? false
             },

bitchatTests/Services/BLEAnnounceHandlerTests.swift

@@ -7,6 +7,8 @@ struct BLEAnnounceHandlerTests {
     private final class Recorder {
         var existingNoisePublicKey: Data?
         var existingSigningPublicKey: Data?
+        var persistedSigningPublicKey: Data?
+        var persistedSigningKeyQueries: [PeerID] = []
         var signatureValid = true
         var linkState: (hasPeripheral: Bool, hasCentral: Bool) = (false, false)
         var upsertResult: BLEPeerAnnounceUpdate? = BLEPeerAnnounceUpdate(isNewPeer: false, wasDisconnected: false, previousNickname: nil)
@@ -37,6 +39,10 @@ struct BLEAnnounceHandlerTests {
             messageTTL: TransportConfig.messageTTLDefault,
             now: { now },
             existingPeerKeys: { _ in (recorder.existingNoisePublicKey, recorder.existingSigningPublicKey) },
+            persistedSigningPublicKey: { peerID in
+                recorder.persistedSigningKeyQueries.append(peerID)
+                return recorder.persistedSigningPublicKey
+            },
             verifySignature: { packet, signingPublicKey in
                 recorder.verifySignatureCalls.append((packet, signingPublicKey))
                 return recorder.signatureValid
@@ -422,6 +428,86 @@ struct BLEAnnounceHandlerTests {
         #expect(recorder.uiEventDeliveries.first?.notifyPeerConnected == false)
     }
 
+    @Test
+    func persistedSigningKeyMismatchWithoutRegistryEntryIsRejected() throws {
+        // Registry has no entry (app restart or offline-peer eviction), but
+        // the persisted cryptographic identity still pins the victim's
+        // signing key. An attacker replaying the victim's noiseKey/peerID
+        // with their own signing key must not be treated as first contact.
+        let now = Date(timeIntervalSince1970: 1_000)
+        let noiseKey = Data(repeating: 0x9D, count: 32)
+        let peerID = PeerID(publicKey: noiseKey)
+        let packet = try makeAnnouncePacket(
+            noisePublicKey: noiseKey,
+            peerID: peerID,
+            timestamp: timestamp(now),
+            signature: Data(repeating: 0xEE, count: 64)
+        )
+
+        let recorder = Recorder()
+        recorder.existingNoisePublicKey = nil
+        recorder.existingSigningPublicKey = nil
+        recorder.persistedSigningPublicKey = Data(repeating: 0x42, count: 32) // victim's persisted pin
+        let handler = makeHandler(recorder: recorder, now: now)
+
+        handler.handle(packet, from: peerID)
+
+        #expect(recorder.persistedSigningKeyQueries == [peerID])
+        #expect(recorder.upsertCalls.isEmpty)
+        #expect(recorder.persistedIdentities.isEmpty)
+        #expect(recorder.topologyUpdates.isEmpty)
+        #expect(recorder.uiEventDeliveries.count == 1)
+        #expect(recorder.uiEventDeliveries.first?.notifyPeerConnected == false)
+    }
+
+    @Test
+    func persistedSigningKeyMatchWithoutRegistryEntryIsAccepted() throws {
+        // Legitimate returning peer: registry entry evicted, persisted pin
+        // matches the announced signing key — accepted like a normal announce.
+        let now = Date(timeIntervalSince1970: 1_000)
+        let noiseKey = Data(repeating: 0x9E, count: 32)
+        let peerID = PeerID(publicKey: noiseKey)
+        let packet = try makeAnnouncePacket(
+            noisePublicKey: noiseKey,
+            peerID: peerID,
+            timestamp: timestamp(now),
+            signature: Data(repeating: 0xEE, count: 64)
+        )
+
+        let recorder = Recorder()
+        // Matches the signing key encoded by makeAnnouncePacket.
+        recorder.persistedSigningPublicKey = Data(repeating: 0x99, count: 32)
+        let handler = makeHandler(recorder: recorder, now: now)
+
+        handler.handle(packet, from: peerID)
+
+        #expect(recorder.upsertCalls.count == 1)
+        #expect(recorder.persistedIdentities.count == 1)
+    }
+
+    @Test
+    func registryPinnedSigningKeySkipsPersistedLookup() throws {
+        let now = Date(timeIntervalSince1970: 1_000)
+        let noiseKey = Data(repeating: 0x9F, count: 32)
+        let peerID = PeerID(publicKey: noiseKey)
+        let packet = try makeAnnouncePacket(
+            noisePublicKey: noiseKey,
+            peerID: peerID,
+            timestamp: timestamp(now),
+            signature: Data(repeating: 0xEE, count: 64)
+        )
+
+        let recorder = Recorder()
+        recorder.existingNoisePublicKey = noiseKey
+        recorder.existingSigningPublicKey = Data(repeating: 0x99, count: 32)
+        let handler = makeHandler(recorder: recorder, now: now)
+
+        handler.handle(packet, from: peerID)
+
+        #expect(recorder.persistedSigningKeyQueries.isEmpty)
+        #expect(recorder.upsertCalls.count == 1)
+    }
+
     @Test
     func registryPinRejectionSkipsTopologyAndIdentityPersistence() throws {
         let now = Date(timeIntervalSince1970: 1_000)
@@ -501,6 +587,7 @@ struct BLEAnnounceHandlerTests {
                 let info = box.registry.info(for: peerID)
                 return (info?.noisePublicKey, info?.signingPublicKey)
             },
+            persistedSigningPublicKey: { _ in nil },
             verifySignature: { packet, signingPublicKey in
                 victim.verifyPacketSignature(packet, publicKey: signingPublicKey)
             },
@@ -574,6 +661,150 @@ struct BLEAnnounceHandlerTests {
         #expect(box.persistedIdentities.count == 2)
     }
 
+    @Test
+    func signingKeyPinSurvivesRegistryEvictionAndRestartEndToEnd() throws {
+        // Real crypto + real persistence: the victim announces and gets
+        // pinned, then the registry entry disappears (offline-peer eviction
+        // via reconcileConnectivity, or app restart which starts with an
+        // empty registry). The attacker replays the victim's
+        // noiseKey/peerID with their own signing key and a valid
+        // self-signature — the persisted identity must still block the
+        // takeover, and must not be overwritten. The victim (same signing
+        // key) must be re-accepted.
+        let victim = NoiseEncryptionService(keychain: MockKeychain())
+        let attacker = NoiseEncryptionService(keychain: MockKeychain())
+        let victimNoiseKey = victim.getStaticPublicKeyData()
+        let peerID = PeerID(publicKey: victimNoiseKey)
+        let now = Date()
+
+        let identityKeychain = MockKeychain()
+        let identityManager = SecureIdentityStateManager(identityKeychain)
+
+        final class RegistryBox {
+            var registry = BLEPeerRegistry()
+        }
+        let box = RegistryBox()
+
+        func makeEnvironment(identityManager: SecureIdentityStateManager) -> BLEAnnounceHandlerEnvironment {
+            BLEAnnounceHandlerEnvironment(
+                localPeerID: { PeerID(str: "0102030405060708") },
+                messageTTL: TransportConfig.messageTTLDefault,
+                now: { now },
+                existingPeerKeys: { peerID in
+                    let info = box.registry.info(for: peerID)
+                    return (info?.noisePublicKey, info?.signingPublicKey)
+                },
+                // Mirrors the BLEService wiring: fall back to the persisted
+                // cryptographic identity.
+                persistedSigningPublicKey: { peerID in
+                    identityManager.getCryptoIdentitiesByPeerIDPrefix(peerID)
+                        .compactMap { $0.signingPublicKey }
+                        .first
+                },
+                verifySignature: { packet, signingPublicKey in
+                    victim.verifyPacketSignature(packet, publicKey: signingPublicKey)
+                },
+                linkState: { _ in (hasPeripheral: true, hasCentral: false) },
+                withRegistryBarrier: { body in body() },
+                upsertVerifiedAnnounce: { peerID, announcement, isConnected, now in
+                    box.registry.upsertVerifiedAnnounce(
+                        peerID: peerID,
+                        nickname: announcement.nickname,
+                        noisePublicKey: announcement.noisePublicKey,
+                        signingPublicKey: announcement.signingPublicKey,
+                        isConnected: isConnected,
+                        now: now
+                    )
+                },
+                shouldEmitReconnectLog: { _, _ in false },
+                updateTopology: { _, _ in },
+                persistIdentity: { announcement in
+                    identityManager.upsertCryptographicIdentity(
+                        fingerprint: announcement.noisePublicKey.sha256Fingerprint(),
+                        noisePublicKey: announcement.noisePublicKey,
+                        signingPublicKey: announcement.signingPublicKey,
+                        claimedNickname: announcement.nickname
+                    )
+                },
+                dedupContains: { _ in true },
+                dedupMarkProcessed: { _ in },
+                deliverAnnounceUIEvents: { _, _, _ in },
+                trackPacketSeen: { _ in },
+                sendAnnounceBack: {},
+                scheduleAfterglow: { _ in }
+            )
+        }
+        let handler = BLEAnnounceHandler(environment: makeEnvironment(identityManager: identityManager))
+
+        func makeSignedAnnounce(nickname: String, signer: NoiseEncryptionService) throws -> BitchatPacket {
+            let announcement = AnnouncementPacket(
+                nickname: nickname,
+                noisePublicKey: victimNoiseKey,
+                signingPublicKey: signer.getSigningPublicKeyData(),
+                directNeighbors: nil
+            )
+            let payload = try #require(announcement.encode())
+            let packet = BitchatPacket(
+                type: MessageType.announce.rawValue,
+                senderID: Data(hexString: peerID.id) ?? Data(),
+                recipientID: nil,
+                timestamp: UInt64(now.timeIntervalSince1970 * 1000),
+                payload: payload,
+                signature: nil,
+                ttl: TransportConfig.messageTTLDefault
+            )
+            return try #require(signer.signPacket(packet))
+        }
+
+        func persistedIdentity() -> CryptographicIdentity? {
+            // queue.sync read; fences the manager's pending barrier writes.
+            identityManager.getCryptoIdentitiesByPeerIDPrefix(peerID).first
+        }
+
+        // 1. Victim announces: pinned in the registry and persisted.
+        handler.handle(try makeSignedAnnounce(nickname: "victim", signer: victim), from: peerID)
+        #expect(box.registry.info(for: peerID)?.signingPublicKey == victim.getSigningPublicKeyData())
+        #expect(persistedIdentity()?.signingPublicKey == victim.getSigningPublicKeyData())
+
+        // 2. Registry entry disappears (eviction / restart).
+        _ = box.registry.remove(peerID)
+        #expect(box.registry.info(for: peerID) == nil)
+
+        // 3. Attacker replay with own signing key: rejected via the persisted
+        //    pin, and neither the registry nor the persisted identity change.
+        handler.handle(try makeSignedAnnounce(nickname: "attacker", signer: attacker), from: peerID)
+        #expect(box.registry.info(for: peerID) == nil)
+        #expect(persistedIdentity()?.signingPublicKey == victim.getSigningPublicKeyData())
+        #expect(identityManager.getSocialIdentity(for: victimNoiseKey.sha256Fingerprint())?.claimedNickname == "victim")
+
+        // 4. Victim re-announces with the same signing key: accepted again.
+        handler.handle(try makeSignedAnnounce(nickname: "victim", signer: victim), from: peerID)
+        #expect(box.registry.info(for: peerID)?.nickname == "victim")
+        #expect(box.registry.info(for: peerID)?.signingPublicKey == victim.getSigningPublicKeyData())
+
+        // 5. Simulated app restart: a fresh identity manager reloads the pin
+        //    from the (mock) keychain, and a fresh registry starts empty. The
+        //    attacker replay is still rejected.
+        identityManager.forceSave()
+        let reloadedManager = SecureIdentityStateManager(identityKeychain)
+        #expect(
+            reloadedManager.getCryptoIdentitiesByPeerIDPrefix(peerID).first?.signingPublicKey
+                == victim.getSigningPublicKeyData()
+        )
+        box.registry = BLEPeerRegistry()
+        let restartedHandler = BLEAnnounceHandler(environment: makeEnvironment(identityManager: reloadedManager))
+        restartedHandler.handle(try makeSignedAnnounce(nickname: "attacker", signer: attacker), from: peerID)
+        #expect(box.registry.info(for: peerID) == nil)
+        #expect(
+            reloadedManager.getCryptoIdentitiesByPeerIDPrefix(peerID).first?.signingPublicKey
+                == victim.getSigningPublicKeyData()
+        )
+
+        // ...while the victim is accepted after the restart.
+        restartedHandler.handle(try makeSignedAnnounce(nickname: "victim", signer: victim), from: peerID)
+        #expect(box.registry.info(for: peerID)?.signingPublicKey == victim.getSigningPublicKeyData())
+    }
+
     private func expectNoSideEffects(_ recorder: Recorder) {
         #expect(recorder.barrierCount == 0)
         #expect(recorder.upsertCalls.isEmpty)

bitchatTests/Services/SecureIdentityStateManagerTests.swift

@@ -79,6 +79,100 @@ final class SecureIdentityStateManagerTests: XCTestCase {
         XCTAssertEqual(matches.first?.signingPublicKey, signingPublicKey)
     }
 
+    func test_upsertCryptographicIdentity_refusesToReplacePinnedSigningKey() async {
+        let manager = SecureIdentityStateManager(MockKeychain())
+        let noisePublicKey = Data(repeating: 0x11, count: 32)
+        let fingerprint = noisePublicKey.sha256Fingerprint()
+        let peerID = PeerID(publicKey: noisePublicKey)
+        let victimSigningKey = Data(repeating: 0x22, count: 32)
+        let attackerSigningKey = Data(repeating: 0x66, count: 32)
+
+        manager.upsertCryptographicIdentity(
+            fingerprint: fingerprint,
+            noisePublicKey: noisePublicKey,
+            signingPublicKey: victimSigningKey,
+            claimedNickname: "victim"
+        )
+        let pinned = await waitUntil {
+            manager.getCryptoIdentitiesByPeerIDPrefix(peerID).first?.signingPublicKey == victimSigningKey
+        }
+        XCTAssertTrue(pinned)
+
+        // Attacker upsert with a different signing key must be refused in
+        // full — signing key AND claimed nickname stay the victim's.
+        manager.upsertCryptographicIdentity(
+            fingerprint: fingerprint,
+            noisePublicKey: noisePublicKey,
+            signingPublicKey: attackerSigningKey,
+            claimedNickname: "attacker"
+        )
+
+        // Synchronous reads fence the manager's pending barrier writes.
+        XCTAssertEqual(
+            manager.getCryptoIdentitiesByPeerIDPrefix(peerID).first?.signingPublicKey,
+            victimSigningKey
+        )
+        XCTAssertEqual(manager.getSocialIdentity(for: fingerprint)?.claimedNickname, "victim")
+
+        // The legitimate peer (same signing key) can still update.
+        manager.upsertCryptographicIdentity(
+            fingerprint: fingerprint,
+            noisePublicKey: noisePublicKey,
+            signingPublicKey: victimSigningKey,
+            claimedNickname: "victim-renamed"
+        )
+        let renamed = await waitUntil {
+            manager.getSocialIdentity(for: fingerprint)?.claimedNickname == "victim-renamed"
+        }
+        XCTAssertTrue(renamed)
+        XCTAssertEqual(
+            manager.getCryptoIdentitiesByPeerIDPrefix(peerID).first?.signingPublicKey,
+            victimSigningKey
+        )
+    }
+
+    func test_cryptographicIdentity_persistsAcrossReinitAndKeepsSigningKeyPin() async {
+        let keychain = MockKeychain()
+        let manager = SecureIdentityStateManager(keychain)
+        let noisePublicKey = Data(repeating: 0x13, count: 32)
+        let fingerprint = noisePublicKey.sha256Fingerprint()
+        let peerID = PeerID(publicKey: noisePublicKey)
+        let victimSigningKey = Data(repeating: 0x24, count: 32)
+        let attackerSigningKey = Data(repeating: 0x77, count: 32)
+
+        manager.upsertCryptographicIdentity(
+            fingerprint: fingerprint,
+            noisePublicKey: noisePublicKey,
+            signingPublicKey: victimSigningKey,
+            claimedNickname: "victim"
+        )
+        let pinned = await waitUntil {
+            manager.getCryptoIdentitiesByPeerIDPrefix(peerID).first?.signingPublicKey == victimSigningKey
+        }
+        XCTAssertTrue(pinned)
+        manager.forceSave()
+
+        // Simulated app restart: the pin must survive and still refuse a
+        // different signing key.
+        let reloaded = SecureIdentityStateManager(keychain)
+        XCTAssertEqual(
+            reloaded.getCryptoIdentitiesByPeerIDPrefix(peerID).first?.signingPublicKey,
+            victimSigningKey
+        )
+
+        reloaded.upsertCryptographicIdentity(
+            fingerprint: fingerprint,
+            noisePublicKey: noisePublicKey,
+            signingPublicKey: attackerSigningKey,
+            claimedNickname: "attacker"
+        )
+        XCTAssertEqual(
+            reloaded.getCryptoIdentitiesByPeerIDPrefix(peerID).first?.signingPublicKey,
+            victimSigningKey
+        )
+        XCTAssertEqual(reloaded.getSocialIdentity(for: fingerprint)?.claimedNickname, "victim")
+    }
+
     func test_setBlocked_clearsFavoriteState() async {
         let manager = SecureIdentityStateManager(MockKeychain())
         let fingerprint = String(repeating: "ab", count: 32)