diff --git a/README.md b/README.md
index 3fd390c..12aaf20 100644
--- a/README.md
+++ b/README.md
@@ -297,6 +297,30 @@ Upstream RPC calls (Stellar/Soroban) are protected by a built-in circuit breaker
 
 Live state is available at `GET /api/v1/circuit-breaker/status`. See [`docs/backend/circuit-breaker.md`](docs/backend/circuit-breaker.md) for full reference.
 
+## New Features
+
+### 1. Authentication Middleware (#55)
+All routes under `/api/v1/admin/*` are protected by JWT authentication.
+- **Header**: `Authorization: Bearer <token>`
+- **Validation**: Ensures token is valid and not expired.
+
+### 2. Event Idempotency (#67)
+The `/api/v1/events` endpoint requires an `Idempotency-Key` header to prevent duplicate processing of the same smart contract event.
+- **Header**: `Idempotency-Key: <unique-uuid-or-hash>`
+- **Behavior**: If a key is seen again within 1 hour, the cached response is returned instead of re-processing.
+
+### 3. Smart-Contract Event Indexer (#70)
+A pipeline for indexing escrow and dispute lifecycle updates from smart contracts.
+- **Endpoint**: `POST /api/v1/events`
+- **Supported Events**: `escrow:created`, `escrow:completed`, `dispute:initiated`, `dispute:resolved`.
+
+## Testing
+
+Run unit and integration tests to verify these features:
+```bash
+npm test
+```
+
 ## License
 
 MIT
diff --git a/src/middleware/auth.test.ts b/src/middleware/auth.test.ts
new file mode 100644
index 0000000..d6fc3f2
--- /dev/null
+++ b/src/middleware/auth.test.ts
@@ -0,0 +1,42 @@
+import { Request, Response, NextFunction } from 'express';
+import jwt from 'jsonwebtoken';
+import { authenticateToken, AuthRequest } from './auth';
+
+describe('authenticateToken', () => {
+  let mockRequest: Partial<AuthRequest>;
+  let mockResponse: Partial<Response>;
+  let nextFunction: NextFunction = jest.fn();
+
+  beforeEach(() => {
+    mockRequest = {
+      headers: {},
+    };
+    mockResponse = {
+      status: jest.fn().mockReturnThis(),
+      json: jest.fn(),
+    };
+  });
+
+  it('should return 401 if no Authorization header is present', () => {
+    authenticateToken(mockRequest as AuthRequest, mockResponse as Response, nextFunction);
+    expect(mockResponse.status).toHaveBeenCalledWith(401);
+    expect(mockResponse.json).toHaveBeenCalledWith({ error: 'Authentication token required' });
+  });
+
+  it('should return 403 for an invalid token', () => {
+    mockRequest.headers!['authorization'] = 'Bearer invalid-token';
+    authenticateToken(mockRequest as AuthRequest, mockResponse as Response, nextFunction);
+    expect(mockResponse.status).toHaveBeenCalledWith(403);
+    expect(mockResponse.json).toHaveBeenCalledWith({ error: 'Invalid authentication token' });
+  });
+
+  it('should call next() for a valid token', () => {
+    const user = { id: 'user-123' };
+    const token = jwt.sign(user, process.env.JWT_SECRET || 'tt-dev-secret-keep-it-safe');
+    mockRequest.headers!['authorization'] = `Bearer ${token}`;
+
+    authenticateToken(mockRequest as AuthRequest, mockResponse as Response, nextFunction);
+    expect(nextFunction).toHaveBeenCalled();
+    expect((mockRequest as AuthRequest).user).toMatchObject(user);
+  });
+});
diff --git a/src/middleware/idempotency.test.ts b/src/middleware/idempotency.test.ts
new file mode 100644
index 0000000..f3404c6
--- /dev/null
+++ b/src/middleware/idempotency.test.ts
@@ -0,0 +1,68 @@
+import { Request, Response, NextFunction } from 'express';
+import { idempotencyMiddleware, clearIdempotencyStore } from './idempotency';
+
+describe('idempotencyMiddleware', () => {
+  let mockRequest: Partial<Request>;
+  let mockResponse: Partial<Response>;
+  let nextFunction: NextFunction;
+
+  beforeEach(() => {
+    mockRequest = {
+      headers: {},
+    };
+    mockResponse = {
+      status: jest.fn().mockReturnThis(),
+      json: jest.fn(),
+      send: jest.fn() as any,
+    };
+    nextFunction = jest.fn();
+    clearIdempotencyStore();
+  });
+
+  it('should return 400 if Idempotency-Key header is missing', () => {
+    idempotencyMiddleware(mockRequest as Request, mockResponse as Response, nextFunction);
+    expect(mockResponse.status).toHaveBeenCalledWith(400);
+    expect(mockResponse.json).toHaveBeenCalledWith({ error: 'Idempotency-Key header is required' });
+  });
+
+  it('should allow operation with new Idempotency-Key', () => {
+    mockRequest.headers!['idempotency-key'] = 'unique-key-1';
+    idempotencyMiddleware(mockRequest as Request, mockResponse as Response, nextFunction);
+    expect(nextFunction).toHaveBeenCalled();
+  });
+
+  it('should return 409 if Idempotency-Key is still in processing status', () => {
+    mockRequest.headers!['idempotency-key'] = 'processing-key';
+    
+    // First call sets it to processing
+    idempotencyMiddleware(mockRequest as Request, mockResponse as Response, nextFunction);
+    
+    // Second call with same key
+    idempotencyMiddleware(mockRequest as Request, mockResponse as Response, nextFunction);
+    expect(mockResponse.status).toHaveBeenCalledWith(409);
+    expect(mockResponse.json).toHaveBeenCalledWith({ error: 'Request is already being processed' });
+  });
+
+  it('should return cached response for completed Idempotency-Key', () => {
+    mockRequest.headers!['idempotency-key'] = 'completed-key';
+    
+    // First call sets it to processing
+    idempotencyMiddleware(mockRequest as Request, mockResponse as Response, nextFunction);
+    
+    const originalBody = { status: 'success', data: { id: 123 } };
+    // Simulate completion
+    (mockResponse.send as any)(JSON.stringify(originalBody));
+
+    // Reset mock response to track new call
+    mockResponse.status = jest.fn().mockReturnThis();
+    mockResponse.json = jest.fn();
+
+    // Replay request
+    idempotencyMiddleware(mockRequest as Request, mockResponse as Response, nextFunction);
+    expect(mockResponse.status).toHaveBeenCalledWith(200);
+    expect(mockResponse.json).toHaveBeenCalledWith({
+      ...originalBody,
+      idempotencyHeader: 'replay-detected'
+    });
+  });
+});
diff --git a/src/middleware/idempotency.ts b/src/middleware/idempotency.ts
new file mode 100644
index 0000000..095b86b
--- /dev/null
+++ b/src/middleware/idempotency.ts
@@ -0,0 +1,70 @@
+import { Request, Response, NextFunction } from 'express';
+
+// Simple in-memory cache for idempotency keys. In a real application, 
+// this should be moved to a persistent store like Redis or a database.
+const idempotencyStore = new Map<string, {
+  status: 'processing' | 'completed';
+  timestamp: number;
+  result?: any;
+}>();
+
+const CACHE_TTL = 3600 * 1000; // 1 hour TTL for idempotency keys
+
+/**
+ * Middleware to enforce idempotency keys for protected operations
+ */
+export const idempotencyMiddleware = (req: Request, res: Response, next: NextFunction) => {
+  const idempotencyKey = req.headers['idempotency-key'] as string;
+
+  if (!idempotencyKey) {
+    return res.status(400).json({ error: 'Idempotency-Key header is required' });
+  }
+
+  // Basic cleanup of old keys (can be optimized or moved to a separate job)
+  const now = Date.now();
+  for (const [key, value] of idempotencyStore.entries()) {
+    if (now - value.timestamp > CACHE_TTL) {
+      idempotencyStore.delete(key);
+    }
+  }
+
+  const existingEntry = idempotencyStore.get(idempotencyKey);
+
+  if (existingEntry) {
+    if (existingEntry.status === 'processing') {
+      return res.status(409).json({ error: 'Request is already being processed' });
+    }
+    
+    // If it's already completed, return its cached result
+    return res.status(existingEntry.status === 'completed' ? 200 : 409).json({
+      ...existingEntry.result,
+      idempotencyHeader: 'replay-detected'
+    });
+  }
+
+  // Pre-register the key to prevent race conditions (basic version)
+  idempotencyStore.set(idempotencyKey, {
+    status: 'processing',
+    timestamp: Date.now()
+  });
+
+  // Proxy the original send method to capture the result
+  const originalSend = res.send;
+  res.send = function (body: any): Response {
+    idempotencyStore.set(idempotencyKey, {
+      status: 'completed',
+      timestamp: Date.now(),
+      result: typeof body === 'string' ? JSON.parse(body) : body
+    });
+    return originalSend.apply(res, arguments as any);
+  };
+
+  next();
+};
+
+/**
+ * Clean up the idempotency store manually (for testing or maintenance)
+ */
+export const clearIdempotencyStore = () => {
+  idempotencyStore.clear();
+};
diff --git a/src/services/indexer.test.ts b/src/services/indexer.test.ts
new file mode 100644
index 0000000..02e0f89
--- /dev/null
+++ b/src/services/indexer.test.ts
@@ -0,0 +1,59 @@
+import { EventIndexerService, EventType, SmartContractEvent } from './indexer';
+
+describe('EventIndexerService', () => {
+  let indexer: EventIndexerService;
+
+  beforeEach(() => {
+    indexer = new EventIndexerService();
+  });
+
+  const sampleEvent: SmartContractEvent = {
+    contractId: '0x123',
+    eventType: EventType.EscrowCreated,
+    payload: { amount: 100 },
+    timestamp: new Date().toISOString()
+  };
+
+  it('should process and index an event', async () => {
+    const result = await indexer.processEvent(sampleEvent);
+    expect(result.status).toBe('indexed');
+    expect(indexer.getEvents()).toHaveLength(1);
+    expect(indexer.getEvents()[0]).toMatchObject(sampleEvent);
+  });
+
+  it('should filter events by contractId', async () => {
+    await indexer.processEvent(sampleEvent);
+    await indexer.processEvent({
+      ...sampleEvent,
+      contractId: '0x456',
+      eventType: EventType.DisputeInitiated
+    });
+
+    const result = indexer.getEventsByContractId('0x123');
+    expect(result).toHaveLength(1);
+    expect(result[0].contractId).toBe('0x123');
+  });
+
+  it('should throw error for invalid event data', async () => {
+    const invalidEvent = { ...sampleEvent, eventType: undefined } as any;
+    await expect(indexer.processEvent(invalidEvent)).rejects.toThrow('Invalid event data');
+  });
+
+  it('should correctly process different event types', async () => {
+    const consoleSpy = jest.spyOn(console, 'log');
+    
+    await indexer.processEvent({
+      ...sampleEvent,
+      eventType: EventType.DisputeInitiated
+    });
+    expect(consoleSpy).toHaveBeenCalledWith(expect.stringContaining('[Indexer] Dispute initiated'));
+
+    await indexer.processEvent({
+      ...sampleEvent,
+      eventType: EventType.DisputeResolved
+    });
+    expect(consoleSpy).toHaveBeenCalledWith(expect.stringContaining('[Indexer] Dispute resolved'));
+
+    consoleSpy.mockRestore();
+  });
+});
diff --git a/src/services/indexer.ts b/src/services/indexer.ts
new file mode 100644
index 0000000..e0e029d
--- /dev/null
+++ b/src/services/indexer.ts
@@ -0,0 +1,77 @@
+import { Response, Request } from 'express';
+
+export enum EventType {
+  EscrowCreated = 'escrow:created',
+  EscrowCompleted = 'escrow:completed',
+  DisputeInitiated = 'dispute:initiated',
+  DisputeResolved = 'dispute:resolved',
+}
+
+export interface SmartContractEvent {
+  contractId: string;
+  eventType: EventType;
+  idempotencyKey?: string;
+  payload: any;
+  timestamp: string;
+}
+
+/**
+ * Service to index smart contract events
+ */
+export class EventIndexerService {
+  private indexedEvents: Map<string, SmartContractEvent> = new Map();
+
+  constructor() {
+    this.indexedEvents = new Map();
+  }
+
+  /**
+   * Process and index a smart contract event
+   */
+  public async processEvent(event: SmartContractEvent): Promise<{ status: string; eventId: string }> {
+    // Pipeline logic: 
+    // 1. Validation (ensure contractId, type exists)
+    // 2. Logic to handle specific event types (e.g., escrow or dispute updates)
+    // 3. Persist (in-memory for now)
+    
+    if (!event.contractId || !event.eventType) {
+      throw new Error('Invalid event data');
+    }
+
+    // Pipeline processing:
+    switch (event.eventType) {
+      case EventType.EscrowCreated:
+        console.log(`[Indexer] New escrow created for contract: ${event.contractId}`);
+        break;
+      case EventType.DisputeInitiated:
+        console.log(`[Indexer] Dispute initiated for contract: ${event.contractId}`);
+        break;
+      case EventType.DisputeResolved:
+        console.log(`[Indexer] Dispute resolved for contract: ${event.contractId}`);
+        break;
+      default:
+        console.log(`[Indexer] Processing generic event: ${event.eventType}`);
+    }
+
+    const eventId = `ev-${Date.now()}-${Math.random().toString(36).substring(7)}`;
+    this.indexedEvents.set(eventId, event);
+    
+    return { status: 'indexed', eventId };
+  }
+
+  /**
+   * Fetch indexed events (for demonstration)
+   */
+  public getEvents() {
+    return Array.from(this.indexedEvents.values());
+  }
+
+  /**
+   * Fetch specific event by contract ID
+   */
+  public getEventsByContractId(contractId: string) {
+    return Array.from(this.indexedEvents.values()).filter(e => e.contractId === contractId);
+  }
+}
+
+export const indexerService = new EventIndexerService();