OTP Authentication (One-Time Password)
A login method where a short-lived single-use code (sent by SMS, app, or email, or generated on-device) proves the user controls a registered factor, replacing or supplementing passwords.
Why it matters
Passwords get reused, phished, and shared, especially on shared shop-floor devices. OTP matters because it removes the stored-secret problem for frontline teams: nothing to remember, nothing to leak in a database dump, and each code dies after use. For field workforces in retail and dealerships, phone-plus-OTP is often both more secure and more usable than passwords.
How it works
The user identifies (typically by phone number), the system generates a code bound to that identity with a short expiry and single-use flag, delivers it, and verifies the entry. Sound implementations rate-limit attempts and sends, hash stored codes, bind verification to a session, and then protect the session token properly (secure storage, rotation). TOTP apps generate codes on-device, avoiding SMS interception for higher-risk uses.
A real-world example
A dealership's sales app onboards staff with phone and OTP: no passwords to forget or share between shifts. Session tokens live in the device's secure store with automatic refresh. When a person leaves, deactivating their number ends access, cleanly, with every session's actions attributed to them in the log.
Common mistakes
- ✗ No rate limiting, letting attackers brute-force codes or drain SMS budgets
- ✗ Long-lived or reusable codes, which quietly become passwords again
- ✗ Treating a verified OTP as the end: unprotected session tokens undo the win
- ✗ Using SMS OTP alone for high-value admin actions where interception matters
Best practices
- ✓ Short expiry, single use, rate limits on both attempts and sends
- ✓ Store only hashed codes; log verification events
- ✓ Protect sessions after login: secure storage, rotation, revocation
- ✓ Escalate to TOTP or additional factors for administrative or high-value access
Frequently asked questions
Is OTP the same as two-factor authentication?
OTP is a factor. Used alone it is single-factor (possession); combined with a password or biometric it forms 2FA. For many frontline flows, possession-based OTP alone already beats shared passwords.
Is SMS OTP secure enough?
For frontline business apps, generally yes with rate limiting and short expiry. For administrator access or high-value transactions, prefer authenticator apps or hardware factors.
Why do field apps prefer phone-plus-OTP?
Zero password reuse, zero sharing between shifts, instant revocation by deactivating the number, and clean per-person attribution in audit logs.
LeadSync signs dealership staff in with phone plus OTP, session tokens in the device secure store, no passwords to leak on a busy showroom floor.
LeadSync's authentication design →