SMS Security: Two-Factor Authentication and OTP Verification

• Something you know (password or PIN)
• Something you have (a phone that receives the OTP)

1. User logs in with email and password.
2. Your app sends an OTP to the user’s phone.
3. User enters the OTP to complete the login.
4. Access is granted only after both steps succeed.

• Login and account recovery
• High-risk actions (password changes, payouts, transfers)
• Phone number verification
• Fraud prevention and identity checks

1. Create a random OTP (6 digits recommended) and store a hashed version with a short expiration time.
2. Send the OTP to the user via SMS.
3. Validate the OTP within the expiration window and invalidate it after a successful match.
4. Limit attempts to reduce brute-force risk.

• Expire OTPs quickly (3 to 5 minutes).
• Lock or throttle after several failed attempts.
• Log and alert on suspicious verification activity.
• Use rate limiting to protect your send endpoints.
• Offer stronger factors for high-security workflows.

POST /api/v1/otp/send_otp
{
  "api_token": "your_api_token",
  "phone_number": "639171234567"
}

POST /api/v1/otp/verify_otp
{
  "api_token": "your_api_token",
  "phone_number": "639171234567",
  "otp": "123456"
}