Migrating from Password to OTP-Based Authentication

One of the most impactful changes I made at Internovo was completely overhauling our authentication system.

The Problem with Passwords

Our users were struggling with:

The Solution: Mobile OTP

I proposed and implemented a mobile OTP-based system:

Flow

Implementation

typescript
// Backend OTP generation
import crypto from 'crypto';

function generateOTP(): string {
  return crypto.randomInt(100000, 999999).toString();
}

// SMS integration
async function sendOTP(mobile: string, otp: string) {
  const response = await smsProvider.send({
    to: mobile,
    message: `Your verification code is: ${otp}`
  });
  
  // Store OTP with expiry
  await redis.set(
    `otp:${mobile}`,
    otp,
    'EX', 300 // 5 minutes
  );
}

// Verification
async function verifyOTP(mobile: string, otp: string): Promise<boolean> {
  const storedOTP = await redis.get(`otp:${mobile}`);
  
  if (!storedOTP || storedOTP !== otp) {
    return false;
  }
  
  await redis.del(`otp:${mobile}`);
  return true;
}

Results

Security Considerations

Rate Limiting

SMS Security

User Feedback

The response was overwhelmingly positive:

> "Finally, I don't have to remember another password!" - Regular user

> "Our support team has 80% fewer password reset tickets." - Support lead

Key Learnings

This migration proved that security and usability don't have to be trade-offs. Sometimes, they go hand in hand.