diff --git a/apps/server/src/routes/setup.ts b/apps/server/src/routes/setup.ts
index 4479b87..4c9f5d7 100644
--- a/apps/server/src/routes/setup.ts
+++ b/apps/server/src/routes/setup.ts
@@ -32,10 +32,15 @@ interface TestBody {
   config: Record<string, string | number | boolean>;
 }
 
-// Config keys that hold device secrets — never sent back to the client. Covers
-// the push Digest password, the rotated device web-UI login, and the Dingtian
-// relay password. Centralised so /state and /assign redact consistently.
-const SECRET_CONFIG_KEYS = ["pushPassword", "webPassword", "relayPassword"] as const;
+// Config keys that hold MACHINE-ONLY secrets — never sent back to the client.
+// No human ever uses these to log in: `pushPassword` is the device→backend Digest
+// secret, `relayPassword` is the binary-protocol relay_pw. They stay redacted.
+//
+// NOTE: the device web-UI login (`webUser`/`webPassword`) is deliberately NOT
+// redacted. It's an operational credential an admin needs to reach the device's
+// own web page, and the whole device-management area is admin-only — so it's
+// surfaced in the admin device view rather than hidden. See first-run-setup.md.
+const SECRET_CONFIG_KEYS = ["pushPassword", "relayPassword"] as const;
 
 function redactSecrets(config: Record<string, unknown>): Record<string, unknown> {
   const out = { ...config };
@@ -157,6 +162,9 @@ export async function setupRoutes(app: FastifyInstance, db: Db): Promise<void> {
 
       const id = randomUUID();
       const fullConfig: Record<string, unknown> = { ...config };
+      // Residual-risk warnings from device hardening (shown to the admin; the
+      // save still succeeds — these are "configured, but note X" advisories).
+      const hardenWarnings: string[] = [];
 
       let device;
       try {
@@ -184,8 +192,14 @@ export async function setupRoutes(app: FastifyInstance, db: Db): Promise<void> {
         }
 
         if (isHardenable(device)) {
-          const { secrets } = await device.harden();
+          const { secrets, warnings } = await device.harden();
           Object.assign(fullConfig, secrets); // e.g. relayPassword
+          // Surface residual-risk warnings (e.g. firmware that won't disable the
+          // password-less string protocol) so the admin can act (web-UI step).
+          for (const w of warnings ?? []) {
+            app.log.warn(`harden(${driverId} ${id}): ${w}`);
+            hardenWarnings.push(w);
+          }
         }
 
         if (hasPushConfig(device)) {
@@ -229,7 +243,11 @@ export async function setupRoutes(app: FastifyInstance, db: Db): Promise<void> {
       };
       await db.insert(laneDevices).values(row);
       // Don't echo device secrets back (push Digest password, web-UI login, …).
-      return reply.code(201).send({ ...row, config: redactSecrets(fullConfig) });
+      return reply.code(201).send({
+        ...row,
+        config: redactSecrets(fullConfig),
+        ...(hardenWarnings.length ? { warnings: hardenWarnings } : {}),
+      });
     },
   );
 
diff --git a/packages/devices/src/drivers/access-dingtian.ts b/packages/devices/src/drivers/access-dingtian.ts
index 1165194..3e7af9c 100644
--- a/packages/devices/src/drivers/access-dingtian.ts
+++ b/packages/devices/src/drivers/access-dingtian.ts
@@ -34,59 +34,37 @@ import { hostField, portField, stubLog } from "./common.js";
 // (input_link_relay). That must be DISABLED on the device for ticket-first
 // entry, else the button opens the barrier before the host can act.
 
-/** Send one UDP datagram and (optionally) await a single reply. */
-function udpRequest(
-  host: string,
-  port: number,
-  payload: string,
-  timeoutMs: number,
-  expectReply: boolean,
-): Promise<string | null> {
-  return new Promise((resolve, reject) => {
-    const sock = createSocket("udp4");
-    let settled = false;
-    const done = (err: Error | null, val: string | null) => {
-      if (settled) return;
-      settled = true;
-      clearTimeout(timer);
-      sock.close();
-      err ? reject(err) : resolve(val);
-    };
-    const timer = setTimeout(
-      () => done(expectReply ? new Error("timeout") : null, null),
-      timeoutMs,
-    );
-    sock.on("error", (e) => done(e, null));
-    sock.on("message", (m) => done(null, m.toString()));
-    sock.bind(() => {
-      sock.send(Buffer.from(payload), port, host, (e) => {
-        if (e) done(e, null);
-        else if (!expectReply) done(null, null);
-      });
-    });
-  });
-}
+// (The string-protocol UDP helper was removed: harden() now disables the
+//  password-less string protocol entirely, and status reads use the
+//  authenticated binary read — see #status() / readStatusFrame.)
 
 /**
  * Send a Dingtian *binary* protocol frame (UDP, default port 60000) and await
- * the reply. Used for relay control because — unlike the string protocol — the
- * binary protocol supports a password (`relay_pw`), so an attacker on a flat
- * network can't fire a relay without it. Frame verified on hardware:
+ * the reply. Used for ALL relay traffic — control AND status read — because,
+ * unlike the string protocol, the binary protocol carries a password (`relay_pw`).
+ * harden() disables the string protocol precisely because it has NO password and
+ * can fire relays (an unauthenticated `"11"` opens relay 1). With the string path
+ * closed, relay_pw actually gates control. Frame verified on hardware:
  *
  *   FF AA <session> <relayCmd> <pwLo> <pwHi> <data...>
  *
  *   FF        = command "set relay"
  *   AA        = result xor (0x00 ^ 0xAA, pc→device)
  *   session   = echoed back
- *   relayCmd  = 1 write, 3 jogging, …
+ *   relayCmd  = 0 read status, 1 write, 3 jogging, …
  *   pwLo,pwHi = relay password, 16-bit LSB-first (0 = none)
  *   data      = command-specific
+ *
+ * NOTE: relay_pw + plaintext UDP is defence-in-depth, NOT a boundary. An attacker
+ * who sniffs the VLAN can replay the password. The real guarantee is the signed
+ * event log (relay open with no signed command = fraud) + VLAN isolation.
  */
 function binaryUdp(
   host: string,
   port: number,
   frame: Buffer,
   timeoutMs: number,
+  localAddress?: string,
 ): Promise<Buffer> {
   return new Promise((resolve, reject) => {
     const sock = createSocket("udp4");
@@ -101,15 +79,33 @@ function binaryUdp(
     const timer = setTimeout(() => done(new Error("timeout"), null), timeoutMs);
     sock.on("error", (e) => done(e, null));
     sock.on("message", (m) => done(null, m));
-    sock.bind(() => {
+    // Bind to a specific local address (the device-facing NIC) on multi-homed
+    // hosts, so the device replies to the right source IP. See net.ts.
+    const onBound = () => {
       sock.send(frame, port, host, (e) => {
         if (e) done(e, null);
       });
-    });
+    };
+    if (localAddress) sock.bind({ address: localAddress }, onBound);
+    else sock.bind(onBound);
   });
 }
 
 let binarySession = 0;
+
+/**
+ * Build a binary "read relay status" frame (relay command 0x00). The device
+ * replies `FF AA <session> 00 <relayBytes> <inputBytes>` (status widths scale
+ * with channel count). This is the *authenticated* status read — unlike the
+ * string protocol's `00`, it carries the relay password, so we can disable the
+ * password-less string protocol entirely. Frame: `FF AA <session> 00 <pwLo> <pwHi>`.
+ * Verified on hardware (4ch): reply `ff aa 00 00 01 0f` = relay1 on, inputs 1111.
+ */
+function readStatusFrame(password: number): Buffer {
+  const session = binarySession++ & 0xff;
+  return Buffer.from([0xff, 0xaa, session, 0x00, password & 0xff, (password >> 8) & 0xff]);
+}
+
 /** Build a binary "write relay with jogging" frame (relay on, auto-off). */
 function jogFrame(channel: number, password: number, jogMs: number): Buffer {
   const session = binarySession++ & 0xff;
@@ -151,9 +147,9 @@ function writeRelayFrame(channel: number, on: boolean, password: number, channel
 const rand16 = () => randomBytes(2).readUInt16BE(0);
 
 /** GET a CGI path on the device's HTTP server and return the raw response text. */
-function cgiGet(host: string, httpPort: number, path: string, timeoutMs: number): Promise<string> {
+function cgiGet(host: string, httpPort: number, path: string, timeoutMs: number, localAddress?: string): Promise<string> {
   return new Promise((resolve, reject) => {
-    const req = httpRequest({ host, port: httpPort, path, method: "GET", timeout: timeoutMs }, (res) => {
+    const req = httpRequest({ host, port: httpPort, path, method: "GET", timeout: timeoutMs, localAddress }, (res) => {
       let data = "";
       res.on("data", (c) => (data += c));
       res.on("end", () => resolve(data));
@@ -186,6 +182,7 @@ function configApi(
   body: string | null,
   timeoutMs: number,
   sessionId?: number, // device session check: sent as Cookie: session=<id>
+  localAddress?: string, // bind outbound to the device-facing NIC (multi-homed hosts)
 ): Promise<string> {
   return new Promise((resolve, reject) => {
     // The device's embedded HTTP server does NOT support chunked request bodies.
@@ -207,6 +204,7 @@ function configApi(
         path,
         method,
         timeout: timeoutMs,
+        localAddress,
         headers: Object.keys(headers).length ? headers : undefined,
       },
       (res) => {
@@ -232,12 +230,15 @@ class DingtianController
 {
   readonly driverId = "dingtian";
   readonly #host: string;
-  readonly #port: number; // string protocol (status read) — UDP 60001
+  readonly #port: number; // legacy string-protocol port (60001) — protocol now disabled by harden(); kept for config compat
   readonly #binaryPort: number; // binary protocol (relay control) — UDP 60000
   readonly #relayPassword: number; // relay_pw (0 = none)
   readonly #sessionId: number; // device CGI session id (0 = session check off)
   readonly #httpPort: number;
   readonly #timeout: number;
+  // Local IP to source outbound device traffic from (the device-facing NIC on a
+  // multi-homed host). undefined = let the OS choose. See net.ts / device-facing-ip.
+  readonly #localAddress: string | undefined;
   readonly #channels: number;
   /** Input level at rest; an input is "active" when it differs from this. */
   readonly #restingHigh: boolean;
@@ -257,6 +258,7 @@ class DingtianController
     this.#relayPassword = config.relayPassword ? Number(config.relayPassword) : 0;
     this.#sessionId = config.sessionId ? Number(config.sessionId) : 0;
     this.#httpPort = config.httpPort ? Number(config.httpPort) : 80;
+    this.#localAddress = config.localAddress ? String(config.localAddress) : undefined;
     this.#timeout = config.timeoutMs ? Number(config.timeoutMs) : 2000;
     this.#channels = config.channels ? Number(config.channels) : 4;
     // This unit idles with inputs HIGH (status "1111"); a press pulls LOW.
@@ -297,14 +299,14 @@ class DingtianController
   async pulseOpen(doorId: number): Promise<void> {
     this.#assertChannel(doorId);
     const frame = jogFrame(doorId, this.#relayPassword, this.#pulseMs);
-    await binaryUdp(this.#host, this.#binaryPort, frame, this.#timeout);
+    await binaryUdp(this.#host, this.#binaryPort, frame, this.#timeout, this.#localAddress);
   }
 
   /** Latch a relay on/off (e.g. for a held-open mode). Channel is 1-based. */
   async setRelay(doorId: number, on: boolean): Promise<void> {
     this.#assertChannel(doorId);
     const frame = writeRelayFrame(doorId, on, this.#relayPassword, this.#channels);
-    await binaryUdp(this.#host, this.#binaryPort, frame, this.#timeout);
+    await binaryUdp(this.#host, this.#binaryPort, frame, this.#timeout, this.#localAddress);
   }
 
   async getDoorStatus(doorId: number): Promise<"open" | "closed"> {
@@ -421,19 +423,30 @@ class DingtianController
   /**
    * Lock the device down for a flat (no-VLAN) network:
    *  - set a random relay password (`relay_pw`) so binary relay commands need it,
-   *  - disable unused protocol channels (rs485/can/tcp×2/mqtt) — keep only UDP1
-   *    binary (relay control) and UDP2 string (status read).
+   *  - keep ONLY UDP1 binary (password-protected relay control + status read),
+   *  - disable every other protocol channel: string, rs485, can, tcp×2, mqtt.
    * Returns the relay password for the backend to persist (required to keep
    * commanding the device afterwards).
    *
+   * SECURITY — why the string protocol (UDP2) is now DISABLED (was a real hole):
+   * the Dingtian string protocol has NO password field and can *fire* relays
+   * (`"11"` = relay 1 on, `"21"` = off, `"11*"` = jog). Leaving it enabled — even
+   * "just for status reads" — let anyone on the network open any barrier with one
+   * unauthenticated UDP packet, completely bypassing relay_pw. Confirmed by
+   * sending `"11"` to port 60001 with no credentials and watching relay 1 close.
+   * So harden() sets udp2.p=255 and status reads move to the authenticated binary
+   * read (relay command 0x00 — see #status()).
+   *
    * NOTE: deliberately does NOT touch the device's HTTP CGI session check
    * (`session_en`). On this firmware enabling it makes the config-read API drop
    * connections, locking us out of the very API we depend on (verified the hard
    * way — required a factory reset). So we leave the config API as-is and rely on
    * relay_pw + fewer open channels + the signed event log.
    *
-   * All are plaintext over HTTP/UDP on a flat network → defence-in-depth, not a
-   * boundary; the signed event log is the real guarantee. See device-input-flow.
+   * Even with the string hole closed, all of this is plaintext over UDP/HTTP →
+   * defence-in-depth, NOT a boundary. The real guarantee is the signed event log
+   * (a relay open with no matching signed command is the fraud signal) plus VLAN
+   * isolation. See device-input-flow / network-isolation.
    */
   async harden(): Promise<HardenResult> {
     const cfg = await this.#readConfig();
@@ -442,17 +455,24 @@ class DingtianController
     const relayPassword = 1 + (rand16() % 9999); // 1..9999 (0 = none)
 
     rc.relay_pw = relayPassword;
-    // Keep UDP1=Binary (p:1) for relay control, UDP2=String (p:0) for status.
-    // Disable everything else (p:255 = None).
+    // Keep ONLY UDP1=Binary (p:1) — it carries relay_pw for both control AND the
+    // status read. Disable everything else (p:255 = None), INCLUDING the string
+    // protocol (udp2), which is password-less and can fire relays.
     (rc.udp1 as Record<string, unknown>).p = 1;
-    (rc.udp2 as Record<string, unknown>).p = 0;
+    (rc.udp2 as Record<string, unknown>).p = 255;
     (rc.rs485 as Record<string, unknown>).p = 255;
     (rc.can as Record<string, unknown>).p = 255;
     (rc.tcpc as Record<string, unknown>).p = 255;
     (rc.tcps as Record<string, unknown>).p = 255;
     (rc.mqtt as Record<string, unknown>).p = 255;
 
-    await this.#writeConfig(cfg, (after) => {
+    // NOTE: udp2 (string protocol) is set to 255 here, but it is NOT part of the
+    // blocking verify. On some firmware (e.g. V3.6J) the CONFIG API silently
+    // refuses to disable udp2 — it accepts the write, reboots, and clamps it back
+    // to enabled — even though every other channel applies and the device's own
+    // web UI CAN disable it. We don't want assign to hard-fail over a firmware
+    // quirk, so we attempt it, then re-check below and warn if it didn't stick.
+    const afterCfg = await this.#writeConfig(cfg, (after) => {
       const a = after.relay_connect as Record<string, unknown> | undefined;
       return (
         a?.relay_pw === relayPassword &&
@@ -463,8 +483,20 @@ class DingtianController
 
     const applied = [
       "set relay password",
-      "disabled rs485/can/tcp/mqtt channels (kept UDP binary + string)",
+      "disabled rs485/can/tcp/mqtt channels (kept password-protected UDP binary)",
     ];
+    const warnings: string[] = [];
+    const stringDisabled =
+      ((afterCfg.relay_connect as Record<string, unknown>)?.udp2 as Record<string, unknown> | undefined)?.p === 255;
+    if (stringDisabled) {
+      applied.push("disabled the password-less string protocol (udp2)");
+    } else {
+      warnings.push(
+        "could not disable the string protocol (udp2) via the config API — this firmware ignores it. " +
+          "An unauthenticated UDP packet to the string port can still fire relays. " +
+          "Disable UDP2 in the device web UI, and rely on VLAN isolation + the signed event log. See dingtian-relay.md.",
+      );
+    }
     const secrets: Record<string, string | number> = { relayPassword };
 
     // Rotate the default admin/admin web login. NOTE: cosmetic — this device's
@@ -483,7 +515,7 @@ class DingtianController
       stubLog(this.driverId, `web-login rotate skipped: ${(err as Error).message}`);
     }
 
-    return { secrets, applied };
+    return { secrets, applied, warnings: warnings.length ? warnings : undefined };
   }
 
   /**
@@ -499,7 +531,7 @@ class DingtianController
     const u = encodeURIComponent(this.#webUser);
     const oldP = encodeURIComponent(this.#webPassword);
     const path = `/userset.cgi?${u}&${oldP}&${u}&${newPassword}&`;
-    const res = await cgiGet(this.#host, this.#httpPort, path, this.#timeout);
+    const res = await cgiGet(this.#host, this.#httpPort, path, this.#timeout, this.#localAddress);
     // "&0&/&" = success; anything else (e.g. "&-5&/&" bad params / wrong old pw).
     const code = res.split("&")[1];
     if (code !== "0") {
@@ -511,7 +543,7 @@ class DingtianController
   // --- config api internals ----------------------------------------------
 
   async #readConfig(): Promise<Record<string, unknown>> {
-    const raw = await configApi(this.#host, this.#httpPort, "/api/v2/config.cgi", "GET", null, this.#timeout, this.#sessionId);
+    const raw = await configApi(this.#host, this.#httpPort, "/api/v2/config.cgi", "GET", null, this.#timeout, this.#sessionId, this.#localAddress);
     return JSON.parse(raw) as Record<string, unknown>;
   }
 
@@ -527,7 +559,7 @@ class DingtianController
   async #writeConfig(
     cfg: Record<string, unknown>,
     verify: (after: Record<string, unknown>) => boolean,
-  ): Promise<void> {
+  ): Promise<Record<string, unknown>> {
     // The set endpoint requires `"command":"setconfig"` injected after `status`
     // (the GET payload omits it). Rebuild preserving node order, command second.
     const out: Record<string, unknown> = {};
@@ -543,7 +575,7 @@ class DingtianController
       // POST. The device resets on apply, so the connection may drop — that's
       // expected, not failure.
       try {
-        await configApi(this.#host, this.#httpPort, "/api/v2/config_set.cgi", "POST", payload, this.#timeout, this.#sessionId);
+        await configApi(this.#host, this.#httpPort, "/api/v2/config_set.cgi", "POST", payload, this.#timeout, this.#sessionId, this.#localAddress);
       } catch {
         // device likely reset on apply
       }
@@ -552,7 +584,8 @@ class DingtianController
       for (let i = 0; i < 12; i++) {
         await sleep(2000);
         try {
-          if (verify(await this.#readConfig())) return; // applied
+          const after = await this.#readConfig();
+          if (verify(after)) return after; // applied — return the landed config
         } catch {
           // still rebooting / unreachable — keep polling
         }
@@ -581,21 +614,35 @@ class DingtianController
     }
   }
 
-  /** Query "00" → parse "0000:1111:4" into relays/inputs/channels. */
+  /**
+   * Read relay + input status via the AUTHENTICATED binary protocol (relay
+   * command 0x00). Reply: `FF AA <session> 00 <relayBytes...> <inputBytes...>`,
+   * each field `ceil(channels/8)` bytes, LSB-first (bit0 → relay/input 1).
+   *
+   * SECURITY: deliberately NOT the string protocol's `00` — that query has no
+   * password field AND the string protocol can also *fire* relays, so leaving it
+   * enabled defeats relay_pw entirely (an attacker sends `"11"` to open relay 1
+   * with no auth). harden() disables the string protocol; status reads come here.
+   */
   async #status(): Promise<DingtianStatus> {
-    const reply = await udpRequest(this.#host, this.#port, "00", this.#timeout, true);
-    if (!reply) throw new Error("dingtian: empty status reply");
-    const [relayStr, inputStr, countStr] = reply.trim().split(":");
-    if (relayStr === undefined || inputStr === undefined) {
-      throw new Error(`dingtian: bad status reply "${reply}"`);
+    const frame = readStatusFrame(this.#relayPassword);
+    const reply = await binaryUdp(this.#host, this.#binaryPort, frame, this.#timeout, this.#localAddress);
+    const width = Math.max(1, Math.ceil(this.#channels / 8));
+    // header: FF AA session 00  (4 bytes) + relay field + input field
+    if (reply.length < 4 + width * 2) {
+      throw new Error(`dingtian: short binary status reply (${reply.length} bytes)`);
     }
-    const bit = (c: string) => c === "1";
-    return {
-      relays: [...relayStr].map(bit),
-      // active = differs from the resting level (press pulls the line).
-      inputs: [...inputStr].map((c) => bit(c) !== this.#restingHigh),
-      channels: countStr ? Number(countStr) : this.#channels,
-    };
+    const relayVal = reply.readUIntLE(4, width);
+    const inputVal = reply.readUIntLE(4 + width, width);
+    const relays: boolean[] = [];
+    const inputs: boolean[] = [];
+    for (let i = 0; i < this.#channels; i++) {
+      const high = (inputVal & (1 << i)) !== 0;
+      relays.push((relayVal & (1 << i)) !== 0);
+      // active = differs from the resting level (a press pulls the line).
+      inputs.push(high !== this.#restingHigh);
+    }
+    return { relays, inputs, channels: this.#channels };
   }
 
   #startPolling(): void {
diff --git a/packages/devices/src/interfaces.ts b/packages/devices/src/interfaces.ts
index 4ccc1f8..9729d0c 100644
--- a/packages/devices/src/interfaces.ts
+++ b/packages/devices/src/interfaces.ts
@@ -142,6 +142,10 @@ export interface HardenResult {
   readonly secrets: Record<string, string | number>;
   /** Human-readable summary of what was changed (for logging/UI). */
   readonly applied: string[];
+  /** Hardening steps that could NOT be applied (e.g. a firmware quirk), so the
+   *  admin knows a residual risk remains. Best-effort steps report here instead
+   *  of failing the whole harden. */
+  readonly warnings?: string[];
 }
 
 export function isHardenable(device: Device): device is Device & HardenableDevice {
diff --git a/wiki/concepts/append-only-event-chain.md b/wiki/concepts/append-only-event-chain.md
index bc9fece..91590f7 100644
--- a/wiki/concepts/append-only-event-chain.md
+++ b/wiki/concepts/append-only-event-chain.md
@@ -24,3 +24,64 @@ It only becomes trustworthy as an external fraud control when paired with [[reco
 against an authority the operator can't alter. Every device event — including those ingested
 from the [[uhppote-controller]] via [[event-log-ingestion]] — should land in this host-side
 chain.
+
+## Implementation (apps/server)
+
+> Implementation-derived. The schema (`packages/db` `events`) and types
+> (`packages/shared` `ParkingEvent`) predate this; the writer/signer are new.
+
+- **`EventLog`** (`apps/server/src/event-log.ts`) is the append primitive. `append()` reads the
+  latest row, sets `index = prev + 1`, `prevHash = sha256(canonical(prev))` (genesis = null),
+  signs the canonical form, and inserts. There are **no update/delete paths**.
+- **Serialized appends.** SQLite is single-writer, but read-prev → compute-hash → insert is
+  multi-step, so `EventLog` also guards it with an in-process async lock — otherwise two near-
+  simultaneous events could claim the same `index` or chain off a stale `prevHash`. Verified:
+  5 concurrent appends produced indices 1..5 with an intact chain.
+- **Canonical form** is a fixed-order JSON array (`index,type,direction,lane,source,identity,
+  occurredAt,prevHash`) — byte-stable, since the chain + signatures depend on it. The volatile
+  row `id` is excluded; chain identity is `index` + content.
+- **`verifyChain()`** walks oldest→newest, recomputing hashes + signatures. Catches tampered
+  content (bad signature), reordering / a deleted row (`index` gap), and a `prevHash` mismatch.
+  Exposed at `GET /api/events/verify` (admin). Read access to the log: `GET /api/events`.
+
+### The `Signer` abstraction (software now, ATECC608 later)
+
+Signing goes through a **`Signer`** interface (`packages/shared`) — the abstraction over the
+[[atecc608]]. Because the chip being wired is still [[open-questions|open-question #6]], the
+server ships a **`SoftwareSigner`** (HMAC-SHA256, key from `EVENT_SIGNING_KEY`). Swapping to the
+secure element is a new `Signer` impl with no `EventLog` change; each event stores its `keyId`
+so old events stay verifiable.
+
+> ⚠️ The software signer makes the chain **self-consistent + tamper-evident**, but **not
+> unforgeable by someone who owns the host** — only the ATECC608's non-extractable key gives
+> property (3) above. Until the chip is wired, the chain detects tampering by *outsiders* and
+> *accidental* corruption, but an operator with the signing key + DB access could re-sign a
+> forged chain. This is the central reason #6 matters.
+
+### What currently feeds the log
+
+Dingtian **input (button) pushes** → bus → `input_received` events (see [[device-input-flow]],
+[[dingtian-relay]]). These are recorded faithfully as raw inputs, **not** as `vehicle_entry` —
+the richer entry event waits for the entry flow (ticket print + barrier command). Device→lane
+mapping is still a TODO (logged with `lane: 0`).
+
+### ⚠️ Limitation: the log captures HOST-ORIGINATED actions only
+
+The event log records what the **host** did (inputs it received, opens it commanded). It is
+**blind to out-of-band relay actuation** — anything that fires a relay without going through the
+host. **Proven on hardware**: a binary relay command sent directly to the device with the
+(sniffable) `relay_pw` fired a relay and produced **zero** events. Out-of-band paths include:
+
+- the **password-less string protocol** (until disabled — see [[dingtian-relay]]),
+- a **sniffed/replayed `relay_pw`** binary command (plaintext UDP — relay control is
+  defence-in-depth, **not** a boundary),
+- the device's own **`ip_watchdog`** (auto-toggles a relay on ping-failure — must stay disabled),
+- a future **`barrier_open_command`** path is host-side and *would* log; these bypass it.
+
+So the log alone does **not** detect operator/attacker fraud at the relay. That is **by design** —
+the actual control is [[reconciliation]]: compare the host's signed *commanded* opens against an
+**independent witness** of opens that physically happened (a door/loop sensor on a Dingtian input
+→ which DOES push + log; the [[lpr-camera]]; payment/Z-report). **A physical open with no matching
+signed command is the fraud signal.** Both the witness sources and the reconciliation logic are
+**NOT yet built** — this is the main open gap. Prevention (VLAN isolation so the attacker can't
+reach UDP 60000) is the necessary first line; detection-via-reconciliation is the backstop.
diff --git a/wiki/entities/dingtian-relay.md b/wiki/entities/dingtian-relay.md
index d4fc452..2360333 100644
--- a/wiki/entities/dingtian-relay.md
+++ b/wiki/entities/dingtian-relay.md
@@ -79,17 +79,42 @@ the relay via UDP. See [[device-input-flow]] for the full path + trust model.
 > real path** — lower latency, and it can be authenticated (the device supports Basic/Digest +
 > HTTPS on the push), unlike the open UDP control direction.
 
+### What it pushes vs. doesn't (logging)
+
+- **Inputs (buttons): YES, pushed.** Input changes are HTTP-pushed via `input_link_url` and now
+  land in the host's signed [[append-only-event-chain]] as `input_received` events (bus →
+  `EventLog`). That is the audit trail for "a button fired."
+- **Relay / barrier opens: NO push, no log.** The device has **no event log of its own** and does
+  not report when a relay fires — relay control is one-way UDP that the *host* initiates. So
+  "the barrier opened" is not something to scrape from the device. The host records what it
+  *commanded* (a future `barrier_open_command` event); a relay open with **no matching signed
+  host event is itself the anomaly** to alarm on ([[threat-model]]). Do not treat the Dingtian as
+  a log source — it is a dumb relay+input board; the host is the source of truth.
+
 ## Hardening (`harden()`) — and why HTTP auth is not a boundary here
 
 On assign the driver runs `harden()` (the [[device-registry|HardenableDevice]] capability):
 1. **`relay_pw`** — set a random relay password so binary relay commands (UDP 60000) need it.
-2. **Disable unused channels** — set `p:255` on rs485/can/tcp×2/mqtt; keep only UDP1 binary
-   (relay control) + UDP2 string (status read).
+2. **Disable EVERY other channel** — set `p:255` on the string protocol (udp2), rs485, can,
+   tcp×2, mqtt; keep **only** UDP1 binary, which carries `relay_pw` for both control AND status.
 3. **Rotate the `admin`/`admin` web login** — `GET /userset.cgi?<old_u>&<old_p>&<new_u>&<new_p>&`
    (response `&0&…&` = success, verified on hardware). The new password is stored back in
    config (`webUser`/`webPassword`) so a re-run can rotate again (the device checks the *old*
    creds). This step is **best-effort** — a failure logs and does not fail the assign.
 
+> ⚠️ **The string protocol (udp2) is a password-less relay-fire path — the original `harden()`
+> left it ENABLED "for status reads", which was a real hole.** The Dingtian string protocol has
+> NO password field and can fire relays (`"11"` = relay 1 on, `"21"` = off, `"11*"` = jog).
+> **Proven on hardware**: sending `"11"` to UDP 60001 with no credentials opened relay 1,
+> completely bypassing `relay_pw`. Fixes: (a) status reads moved to the **authenticated binary
+> read** (relay command `0x00`) so the string protocol is no longer needed; (b) `harden()` now
+> sets `udp2.p=255` to disable it. **Firmware caveat (V3.6J):** the CONFIG API silently refuses
+> to disable udp2 — it accepts the write, reboots, and clamps it back — even though the device's
+> **web UI can** disable it. So the udp2 disable is **best-effort + warns** (it is NOT part of the
+> blocking verify); if it doesn't stick, `harden()` returns a warning telling the admin to flip
+> UDP2 off in the device web UI. Verified: after the web-UI disable, the `"11"` attack gets no
+> reply and the relay stays off, while authenticated binary control/status still work.
+
 > ⚠️ **The device CGI API is UNAUTHENTICATED.** Verified on hardware: `GET /api/v2/config.cgi`,
 > `/`, and even `/userset.cgi` all return **200 with no credentials**. The `admin`/`admin` login
 > gates only the interactive **browser UI** — the CGI control plane (read/write full config, fire
diff --git a/wiki/log.md b/wiki/log.md
index 0b40587..767c42a 100644
--- a/wiki/log.md
+++ b/wiki/log.md
@@ -238,3 +238,39 @@ guarantee. Recorded in [[dingtian-relay]] (new Hardening section).
 - Verified via Fastify inject: 2 printers assigned to one lane -> both listed, no secret leak,
   delete -> 204, delete unknown -> 404, count drops to 1. Full repo typechecks (8/8).
 - Updated [[first-run-setup]].
+
+## [2026-06-15] ingest | Append-only signed event log (Dingtian input pushes persist)
+- Q: does the Dingtian push events? -> inputs YES (input_link_url), relay opens NO (device keeps
+  no log). Host is the source of truth; a relay open w/o matching signed event is the anomaly.
+- Implemented EventLog (apps/server/event-log.ts): serialized append, monotonic index, prevHash
+  chain, signature; verifyChain() detects tamper/reorder/delete. Read: GET /api/events;
+  integrity: GET /api/events/verify (admin).
+- Signer abstraction (packages/shared) over the ATECC608; SoftwareSigner (HMAC, EVENT_SIGNING_KEY)
+  shipped now since chip wiring is open-question #6. Caveat documented: software signer is
+  tamper-evident but NOT unforgeable-by-owner.
+- Wired bus -> log: Dingtian input pushes become input_received events (lane mapping TODO).
+- Added ParkingEventType 'input_received'.
+- Verified via inject: push w/o digest -> 401; pushes -> 2 signed+chained events; verify -> ok;
+  direct DB tamper -> verifyChain catches at the right index; deleted row -> index gap. 5 concurrent
+  appends -> indices 1..5 intact. Full repo typechecks.
+- Updated [[append-only-event-chain]], [[dingtian-relay]].
+
+## [2026-06-15] ingest | Event log + Dingtian string-protocol security fix
+- Append-only signed event log shipped (EventLog, Signer abstraction over ATECC608 w/ SoftwareSigner
+  HMAC; GET /api/events + /api/events/verify). Dingtian input pushes persist as input_received.
+  Verified on hardware: shorting I1-I4 -> 8 signed+chained events, verifyChain ok.
+- SECURITY (verified on hardware): the password-less string protocol (udp2) can fire relays
+  ("11" -> relay1 on) with NO auth, bypassing relay_pw. Fixes: status reads moved to authenticated
+  binary read (cmd 0x00); harden() disables udp2 BEST-EFFORT (firmware V3.6J config API refuses,
+  but web UI works) and returns a warning instead of throwing. After web-UI disable, the "11" attack
+  is dead and binary control/status still work.
+- GAP (user-identified): event log captures host-originated actions only; out-of-band relay
+  actuation (sniffed relay_pw, string protocol, ip_watchdog) produces NO event — proven on hardware.
+  Real control is reconciliation vs. an independent witness; witness+reconciliation NOT yet built.
+- Device web login (webUser/webPassword) now un-redacted in setup state (admin-only device area);
+  pushPassword/relayPassword stay machine-only.
+- harden() warnings surfaced via the assign response.
+- localAddress threaded through the Dingtian driver (device-facing-IP foundation; multi-homed hosts).
+- INCIDENT: probing default.cgi factory-reset the bench device (now at 192.168.1.100, defaults).
+  Re-provisioning is the ADMIN's job via First-run setup (app must not hardcode site IPs).
+- Updated [[append-only-event-chain]], [[dingtian-relay]].