OTP for Crypto Exchanges & Web3 Apps in India

Crypto exchanges and Web3 apps have a different risk profile than regular fintech: a single account compromise can drain a wallet instantly and irreversibly. SMS OTP is still part of the stack for good reasons — but it’s not enough on its own.

Why OTP at All for Crypto

• Universal: every Indian phone supports SMS, no app install needed.
• Low friction at signup: lower drop-off than asking for an authenticator app.
• Anchors a real identity to every account.
• Cheap: Rs 0.25 per OTP scales to millions of users.

Where OTP Fits

• Initial signup and email/phone confirmation.
• Login from a new device (paired with device fingerprint).
• Re-confirming identity for view-only changes (default address, profile).
• Account recovery (paired with KYC re-check).

Where OTP Fails

For withdrawal authorization, security setting changes, and whitelisting new wallet addresses, SMS OTP is not enough. SIM swap is the dominant attack: see our SIM swap defense article. Treat these flows as “require TOTP or hardware key.”

Recommended Auth Stack

1. Phone OTP at signup and on every login from a new device.
2. TOTP authenticator mandatory for any user who completes KYC and deposits funds.
3. Withdrawal whitelist with 24-hour cooling period and TOTP confirmation when adding addresses.
4. Hardware key (FIDO2) optional for power users; some exchanges offer fee discounts for FIDO2 users.
5. Device binding across all of the above so a stolen credential alone can’t move funds.

Indian Regulatory Context

Indian crypto exchanges operate under FIU registration and strict AML / CFT rules. Phone OTP plays a small but important role: it gives auditors a clean trail of which phone confirmed which action. Pair it with PAN and Aadhaar verification for the full KYC picture.

Integration Notes

1. Lead the SMS body with the action (“Withdraw Rs ...”).
2. Never include the destination wallet address in the SMS.
3. Rate-limit OTP send by phone and IP — see our rate limiting guide.
4. Log every verification with request ID, IP, and device fingerprint for the compliance team.

FAQ

See our fintech OTP guide for the related architecture.