diff --git a/docker-compose.yml b/docker-compose.yml
index ee7fd472..46b50904 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -75,7 +75,6 @@ services:
     restart: on-failure
     networks:
       default:
-        ipv4_address: 10.10.10.2
 
   nostream-db:
     image: postgres:15
diff --git a/src/@types/adapters.ts b/src/@types/adapters.ts
index 130d7853..88bfd081 100644
--- a/src/@types/adapters.ts
+++ b/src/@types/adapters.ts
@@ -15,6 +15,7 @@ export type IWebSocketAdapter = EventEmitter & {
   getClientId(): string
   getClientAddress(): string
   getSubscriptions(): Map<string, SubscriptionFilter[]>
+  getChallenge(): string
 }
 
 export interface ICacheAdapter {
diff --git a/src/@types/messages.ts b/src/@types/messages.ts
index f95538f8..bdfe9244 100644
--- a/src/@types/messages.ts
+++ b/src/@types/messages.ts
@@ -12,13 +12,14 @@ export enum MessageType {
   OK = 'OK',
   COUNT = 'COUNT',
   CLOSED = 'CLOSED',
+  AUTH = 'AUTH',
 }
 
-export type IncomingMessage = (SubscribeMessage | IncomingEventMessage | UnsubscribeMessage | CountMessage) & {
+export type IncomingMessage = (SubscribeMessage | IncomingEventMessage | UnsubscribeMessage | CountMessage | AuthMessage) & {
   [ContextMetadataKey]?: ContextMetadata
 }
 
-export type OutgoingMessage = OutgoingEventMessage | EndOfStoredEventsNotice | NoticeMessage | CommandResult | CountResultMessage | ClosedMessage
+export type OutgoingMessage = OutgoingEventMessage | EndOfStoredEventsNotice | NoticeMessage | CommandResult | CountResultMessage | ClosedMessage | AuthChallengeMessage
 
 export type SubscribeMessage = {
   [index in Range<2, 100>]: SubscriptionFilter
@@ -89,3 +90,13 @@ export interface ClosedMessage {
   1: SubscriptionId
   2: string
 }
+
+export interface AuthMessage {
+  0: MessageType.AUTH
+  1: Event
+}
+
+export interface AuthChallengeMessage {
+  0: MessageType.AUTH
+  1: string
+}
diff --git a/src/adapters/web-socket-adapter.ts b/src/adapters/web-socket-adapter.ts
index 989c6083..5706eb00 100644
--- a/src/adapters/web-socket-adapter.ts
+++ b/src/adapters/web-socket-adapter.ts
@@ -3,9 +3,10 @@ import { EventEmitter } from 'stream'
 import { IncomingMessage as IncomingHttpMessage } from 'http'
 import { WebSocket } from 'ws'
 import { ZodError } from 'zod'
+import { randomBytes } from 'crypto'
 
 import { ContextMetadata, Factory } from '../@types/base'
-import { createNoticeMessage, createOutgoingEventMessage } from '../utils/messages'
+import { createAuthChallengeMessage, createNoticeMessage, createOutgoingEventMessage } from '../utils/messages'
 import { IAbortable, IMessageHandler } from '../@types/message-handlers'
 import { IncomingMessage, OutgoingMessage } from '../@types/messages'
 import { IWebSocketAdapter, IWebSocketServerAdapter } from '../@types/adapters'
@@ -32,6 +33,7 @@ export class WebSocketAdapter extends EventEmitter implements IWebSocketAdapter
   private clientAddress: SocketAddress
   private alive: boolean
   private subscriptions: Map<SubscriptionId, SubscriptionFilter[]>
+  private challenge: string
 
   public constructor(
     private readonly client: WebSocket,
@@ -79,6 +81,13 @@ export class WebSocketAdapter extends EventEmitter implements IWebSocketAdapter
       .on(WebSocketAdapterEvent.Message, this.sendMessage.bind(this))
 
     logger('client %s connected from %s', this.clientId, this.clientAddress.address)
+
+    this.challenge = randomBytes(16).toString('hex')
+    this.sendMessage(createAuthChallengeMessage(this.challenge))
+  }
+
+  public getChallenge(): string {
+    return this.challenge
   }
 
   public getClientId(): string {
diff --git a/src/constants/base.ts b/src/constants/base.ts
index 4c8c6cf6..154f23bb 100644
--- a/src/constants/base.ts
+++ b/src/constants/base.ts
@@ -40,6 +40,7 @@ export enum EventKinds {
   PARAMETERIZED_REPLACEABLE_FIRST = 30000,
   PARAMETERIZED_REPLACEABLE_LAST = 39999,
   USER_APPLICATION_FIRST = 40000,
+  AUTH = 22242,
 }
 
 export enum EventTags {
@@ -52,6 +53,7 @@ export enum EventTags {
   Invoice = 'bolt11',
   // NIP-03: target event kind on an OpenTimestamps attestation
   Kind = 'k',
+  Challenge = 'challenge',
 }
 
 export const ALL_RELAYS = 'ALL_RELAYS'
diff --git a/src/factories/message-handler-factory.ts b/src/factories/message-handler-factory.ts
index 273b5b37..b6943725 100644
--- a/src/factories/message-handler-factory.ts
+++ b/src/factories/message-handler-factory.ts
@@ -2,6 +2,7 @@ import { ICacheAdapter, IWebSocketAdapter } from '../@types/adapters'
 import { IEventRepository, INip05VerificationRepository, IUserRepository } from '../@types/repositories'
 import { IncomingMessage, MessageType } from '../@types/messages'
 import { createSettings } from './settings-factory'
+import { AuthMessageHandler } from '../handlers/auth-message-handler'
 import { CountMessageHandler } from '../handlers/count-message-handler'
 import { EventMessageHandler } from '../handlers/event-message-handler'
 import { eventStrategyFactory } from './event-strategy-factory'
@@ -45,6 +46,8 @@ export const messageHandlerFactory =
         return new UnsubscribeMessageHandler(adapter)
       case MessageType.COUNT:
         return new CountMessageHandler(adapter, eventRepository, createSettings)
+      case MessageType.AUTH:
+        return new AuthMessageHandler(adapter, createSettings)
       default:
         throw new Error(`Unknown message type: ${String(message[0]).substring(0, 64)}`)
     }
diff --git a/src/handlers/auth-message-handler.ts b/src/handlers/auth-message-handler.ts
new file mode 100644
index 00000000..b894a9c2
--- /dev/null
+++ b/src/handlers/auth-message-handler.ts
@@ -0,0 +1,56 @@
+import { EventKinds, EventTags } from '../constants/base'
+import { IMessageHandler } from '../@types/message-handlers'
+import { isEventIdValid, isEventSignatureValid } from '../utils/event'
+import { AuthMessage } from '../@types/messages'
+import { createLogger } from '../factories/logger-factory'
+import { Factory } from '../@types/base'
+import { IWebSocketAdapter } from '../@types/adapters'
+import { Settings } from '../@types/settings'
+
+const logger = createLogger('auth-message-handler')
+
+export class AuthMessageHandler implements IMessageHandler {
+  public constructor(
+    private readonly webSocket: IWebSocketAdapter,
+    private readonly settings: Factory<Settings>,
+  ) {}
+
+  public async handleMessage(message: AuthMessage): Promise<void> {
+    const event = message[1]
+    const clientId = this.webSocket.getClientId()
+
+    if (event.kind !== EventKinds.AUTH) {
+      logger('client %s sent invalid auth event kind: %d', clientId, event.kind)
+      return
+    }
+
+    const isValid = (await isEventIdValid(event)) && (await isEventSignatureValid(event))
+    if (!isValid) {
+      logger('client %s sent invalid auth event signature: %s', clientId, event.id)
+      return
+    }
+
+    const challenge = event.tags.find((tag) => tag[0] === EventTags.Challenge)?.[1]
+    if (challenge !== this.webSocket.getChallenge()) {
+      logger('client %s sent invalid auth challenge: expected %s, got %s', clientId, this.webSocket.getChallenge(), challenge)
+      return
+    }
+
+    const relay = event.tags.find((tag) => tag[0] === EventTags.Relay)?.[1]
+    const configuredRelayUrl = this.settings().info.relay_url
+    if (relay !== configuredRelayUrl) {
+      logger('client %s sent invalid auth relay: expected %s, got %s', clientId, configuredRelayUrl, relay)
+      return
+    }
+
+    // NIP-42: event must be recent (e.g., within 10 minutes)
+    const now = Math.floor(Date.now() / 1000)
+    if (Math.abs(event.created_at - now) > 600) {
+      logger('client %s sent expired auth event: %d (now: %d)', clientId, event.created_at, now)
+      return
+    }
+
+    // In a real implementation, we would associate the pubkey with the client session.
+    logger('client %s authenticated as %s', clientId, event.pubkey)
+  }
+}
diff --git a/src/schemas/message-schema.ts b/src/schemas/message-schema.ts
index 53b8f09f..0a18ad8d 100644
--- a/src/schemas/message-schema.ts
+++ b/src/schemas/message-schema.ts
@@ -55,4 +55,6 @@ export const countMessageSchema = z
 
 export const closeMessageSchema = z.tuple([z.literal(MessageType.CLOSE), subscriptionSchema])
 
-export const messageSchema = z.union([eventMessageSchema, reqMessageSchema, closeMessageSchema, countMessageSchema])
+export const authMessageSchema = z.tuple([z.literal(MessageType.AUTH), eventSchema])
+
+export const messageSchema = z.union([eventMessageSchema, reqMessageSchema, closeMessageSchema, countMessageSchema, authMessageSchema])
diff --git a/src/utils/messages.ts b/src/utils/messages.ts
index 0b98d5f4..bc751a78 100644
--- a/src/utils/messages.ts
+++ b/src/utils/messages.ts
@@ -1,4 +1,5 @@
 import {
+  AuthChallengeMessage,
   ClosedMessage,
   CountResultMessage,
   CountResultPayload,
@@ -41,6 +42,10 @@ export const createClosedMessage = (queryId: SubscriptionId, reason: string): Cl
   return [MessageType.CLOSED, queryId, reason]
 }
 
+export const createAuthChallengeMessage = (challenge: string): AuthChallengeMessage => {
+  return [MessageType.AUTH, challenge]
+}
+
 export const createSubscriptionMessage = (
   subscriptionId: SubscriptionId,
   filters: SubscriptionFilter[],
diff --git a/task3.js b/task3.js
new file mode 100644
index 00000000..37c7086c
--- /dev/null
+++ b/task3.js
@@ -0,0 +1,83 @@
+const WebSocket = require('ws');
+const secp256k1 = require('@noble/secp256k1');
+const crypto = require('crypto');
+
+/**
+ * Task 3: Standalone Node.js script that connects to a relay,
+ * receives an AUTH challenge, constructs a valid kind 22242 event,
+ * and sends it back.
+ */
+async function solveTask3() {
+    const relayUrl = 'ws://localhost:8008';
+    const ws = new WebSocket(relayUrl);
+
+    // Generate a temporary keypair for the demo
+    const privKey = secp256k1.utils.randomPrivateKey();
+    const pubKey = secp256k1.utils.bytesToHex(secp256k1.getPublicKey(privKey, true).subarray(1));
+
+    console.log('Connecting to', relayUrl, '...');
+
+    ws.on('open', () => {
+        console.log('Connected to relay');
+    });
+
+    ws.on('message', async (data) => {
+        const message = JSON.parse(data.toString());
+        console.log('Received from relay:', message);
+
+        if (message[0] === 'AUTH' && typeof message[1] === 'string') {
+            const challenge = message[1];
+            console.log('>>> Received AUTH challenge:', challenge);
+
+            // Construct kind 22242 event (NIP-42)
+            const event = {
+                pubkey: pubKey,
+                created_at: Math.floor(Date.now() / 1000),
+                kind: 22242,
+                tags: [
+                    ['relay', relayUrl],
+                    ['challenge', challenge]
+                ],
+                content: ''
+            };
+
+            // Calculate ID (Hash)
+            const serialized = JSON.stringify([
+                0,
+                event.pubkey,
+                event.created_at,
+                event.kind,
+                event.tags,
+                event.content
+            ]);
+            const id = crypto.createHash('sha256').update(serialized).digest('hex');
+            event.id = id;
+
+            // Sign event
+            console.log('Signing event...');
+            const sig = await secp256k1.schnorr.sign(event.id, privKey);
+            event.sig = secp256k1.utils.bytesToHex(sig);
+
+            // Send back
+            const authResponse = JSON.stringify(['AUTH', event]);
+            console.log('>>> Sending AUTH response:', authResponse);
+            ws.send(authResponse);
+            
+            // Wait a bit to see if we get a response (though NIP-42 doesn't mandate one)
+            setTimeout(() => {
+                console.log('Closing connection...');
+                ws.close();
+            }, 2000);
+        }
+    });
+
+    ws.on('error', (err) => {
+        console.error('WebSocket error:', err);
+    });
+
+    ws.on('close', () => {
+        console.log('Connection closed');
+    });
+}
+
+solveTask3().catch(console.error);
diff --git a/task4.ts b/task4.ts
new file mode 100644
index 00000000..c0038478
--- /dev/null
+++ b/task4.ts
@@ -0,0 +1,30 @@
+import * as secp256k1 from '@noble/secp256k1';
+
+/**
+ * Verifies a Nostr event signature.
+ * 
+ * @param event The Nostr event object containing id, pubkey, and sig.
+ * @returns A promise that resolves to true if the signature is valid, false otherwise.
+ */
+export async function verifyEventSignature(event: {
+  id: string;
+  pubkey: string;
+  sig: string;
+}): Promise<boolean> {
+  try {
+    return await secp256k1.schnorr.verify(event.sig, event.id, event.pubkey);
+  } catch (error) {
+    console.error('Signature verification failed:', error);
+    return false;
+  }
+}
+
+// Example usage (uncomment to test):
+/*
+const mockEvent = {
+  id: '...', // hex string
+  pubkey: '...', // hex string
+  sig: '...', // hex string
+};
+verifyEventSignature(mockEvent).then(console.log);
+*/
diff --git a/test/unit/adapters/web-socket-adapter.spec.ts b/test/unit/adapters/web-socket-adapter.spec.ts
index a6517509..b38fe87b 100644
--- a/test/unit/adapters/web-socket-adapter.spec.ts
+++ b/test/unit/adapters/web-socket-adapter.spec.ts
@@ -77,6 +77,7 @@ describe('WebSocketAdapter', () => {
       slidingWindowRateLimiter,
       settingsFactory,
     )
+    client.send.resetHistory()
   })
 
   afterEach(() => {
diff --git a/test_task4.ts b/test_task4.ts
new file mode 100644
index 00000000..60713702
--- /dev/null
+++ b/test_task4.ts
@@ -0,0 +1,34 @@
+import { verifyEventSignature } from './task4';
+import * as secp256k1 from '@noble/secp256k1';
+import * as crypto from 'crypto';
+
+async function testTask4() {
+  const privKey = '0000000000000000000000000000000000000000000000000000000000000001';
+  const pubKey = secp256k1.utils.bytesToHex(secp256k1.getPublicKey(privKey, true).subarray(1));
+  
+  const event: any = {
+    pubkey: pubKey,
+    created_at: Math.floor(Date.now() / 1000),
+    kind: 1,
+    tags: [],
+    content: 'Test content',
+  };
+
+  const serialized = JSON.stringify([
+    0,
+    event.pubkey,
+    event.created_at,
+    event.kind,
+    event.tags,
+    event.content
+  ]);
+  event.id = crypto.createHash('sha256').update(serialized).digest('hex');
+  
+  const sig = await secp256k1.schnorr.sign(event.id, privKey);
+  event.sig = secp256k1.utils.bytesToHex(sig);
+
+  const isValid = await verifyEventSignature(event);
+  console.log('Is generated event signature valid?', isValid);
+}
+
+testTask4().catch(console.error);