Where fintech uses OTP
In a financial product, a one-time code can confirm access to a channel, but it should not independently decide whether a transaction is safe.
| Journey | OTP role | Additional checks |
|---|---|---|
| Login | Confirm access before session creation | Device, login history, risk |
| Recovery | Allow limited account recovery | End old sessions, notify user |
| New beneficiary | Confirm a sensitive change | Recipient, amount, behavior |
| Payment or transfer | Confirm user intent | Balance, limits, anti-fraud, authorization |
| Detail change | Confirm sensitive account updates | Recent authentication and session |
| API-key issuance | Add step-up verification | Role, scope, and audit |
Your system makes the final decision after all checks. Cascade handles OTP delivery and verification, not financial risk scoring.
Bind the code to an action
Do not accept a code by phone alone. Use a distinct purpose such as login, new_beneficiary, or payment_confirmation, and keep a server-side challenge bound to the exact operation.
Do not treat amount, recipient, or other parameters from the client as the source of truth. Load them from protected server state and validate them again before completion.
Server-side flow
- The user completes primary authentication.
- The backend evaluates risk and decides whether OTP is required.
- The server creates a limited transaction challenge.
- Cascade receives phone, purpose, and an available channel.
- The user enters the code.
- The backend verifies it with the same phone and purpose.
- After
success: true, the system revalidates transaction state before execution.
This final check protects against changes to amount, recipient, or permissions between send and verify.
Channels and cost
WhatsApp and Telegram are publicly available at 3 credits per successful delivery. A new account receives 1000 starting credits. SMS is represented technically with separate post-launch pricing, but the public provider is not live.
Do not display SMS as active fallback before it is enabled. Show users only a channel that actually works.
Limits and security
Fintech flows need independent send and verify limits, controls by phone, account, IP, device, and API key, short expiration, single use, resend cooldown, neutral responses, redacted logs, anomaly alerts, and rapid key rotation.
See the OTP security and rate-limit guides for implementation details.
Audit and observability
Record request ID, internal challenge ID, purpose, technical result, timestamp, and channel. Never store a plaintext OTP or Bearer token.
Measure send, delivery, verification, and transaction completion separately. Successful delivery does not mean that a transaction was successful or safe.
Pilot plan
Start with a lower-risk journey such as test-user login. Exercise valid code, invalid code, expiration, resend, limits, and API-key revocation. Then simulate a transaction changing between send and verify.
Run an internal security review before production and define where OTP alone is insufficient.