Published 2026-06-23 · by Bharosa SMS · Tags: #OTP #Security #Best Practices
One-time passwords are only secure if implemented correctly. This guide covers the best practices Nepal developers and businesses should follow.
OTPs should expire within 3–5 minutes. Longer expiry windows increase the risk of replay attacks.
Allow only 3–5 attempts per OTP. After that, require the user to request a new code.
Prevent abuse by limiting how many OTPs can be sent to the same number within an hour.
If SMS delivery fails, offer voice OTP as a fallback to maintain conversion rates.
Store API keys securely, use HTTPS and validate server-side. Never expose keys in client-side code.
Most security experts recommend 3–5 minutes.
Limit to 3–5 attempts before requiring a new OTP.
SIM swap and SS7 attacks are possible but rare. Combine OTP with device binding for high-security apps.