OTP Data Privacy: DPDP Act Compliance

India's Digital Personal Data Protection (DPDP) Act has changed how businesses must handle personal data, and that includes phone numbers used for OTP verification. If your application sends OTPs to Indian phone numbers, you are processing personal data under the DPDP Act, and you have specific obligations.

This guide explains what the DPDP Act means for developers implementing OTP-based verification, what you need to do to stay compliant, and how choosing the right OTP provider can simplify your compliance posture.

DPDP Act Overview

The Digital Personal Data Protection Act, 2023, is India's comprehensive data protection legislation. It governs the processing of digital personal data within India and applies to any entity that collects, stores, or processes personal data of individuals in India, regardless of where the entity is incorporated.

Key concepts defined by the Act:

• Data Principal — the individual whose personal data is being processed (your end user)
• Data Fiduciary — the entity that determines the purpose and means of processing (your company)
• Data Processor — an entity that processes data on behalf of the Data Fiduciary (your OTP provider, like StartMessaging)
• Personal Data — any data about an individual who is identifiable by or in relation to such data
• Consent — free, specific, informed, unconditional, and unambiguous indication of the Data Principal's wishes

The DPDP Act works alongside TRAI's existing telecom regulations. While TRAI governs the mechanics of SMS delivery (DLT, templates, scrubbing), the DPDP Act governs how you handle the personal data involved in that process. For current TRAI rules, see our article on TRAI SMS regulations in 2026.

Phone Numbers as Personal Data

Under the DPDP Act, phone numbers are classified as personal data. This is unambiguous: a mobile number can identify an individual, making it personal data by definition. When your application collects a phone number for OTP verification, you are collecting personal data.

This classification has several implications:

• Lawful purpose required — you must have a legitimate reason to collect and process the phone number. OTP verification for authentication is a valid lawful purpose.
• Notice obligation — you must inform the user about what data you collect, why you collect it, and how you process it, typically through a privacy policy.
• Purpose limitation — if you collect a phone number for OTP verification, you cannot use it for marketing without separate consent.
• Storage limitation — you must not retain the phone number longer than necessary for the purpose it was collected.
• Security safeguards — you must implement reasonable security measures to protect stored phone numbers from breaches.

OTP Codes Themselves

While the DPDP Act does not specifically address OTP codes, best practice is to treat them with the same care as personal data. An OTP code, combined with a phone number, provides access to an account. OTP codes should be hashed (never stored in plaintext), time-limited, and deleted after use or expiry.

StartMessaging follows this principle by bcrypt-hashing all OTP codes server-side. The plaintext OTP exists only during the brief moment it is sent via SMS and never persists in our systems.

Consent for OTP Delivery

Consent under the DPDP Act must be free, specific, informed, and unambiguous. For OTP delivery, the consent model depends on the context:

Registration and Login OTPs

When a user enters their phone number on your signup or login page and clicks "Send OTP," they are providing consent to receive an OTP message. This is generally considered valid consent under the DPDP Act because:

• The user initiated the action voluntarily (free)
• The purpose is clear — phone verification (specific)
• The user knows an SMS will be sent (informed)
• The user clicked a button to trigger it (unambiguous)

Transaction OTPs

OTPs sent for transaction verification (payment confirmation, bank transfers) are generally covered under the "legitimate use" provisions. When a user initiates a transaction, the OTP is part of the security mechanism they implicitly consent to by using the service.

What Requires Separate Consent

If you want to use the phone number collected for OTP verification to send marketing messages, promotional offers, or other non-transactional communications, you need separate, explicit consent. This consent must be:

• Obtained through a separate action (not bundled with OTP consent)
• Clearly documented and stored
• Easy to withdraw at any time

This is also where TRAI's regulations intersect: promotional messages require DLT compliance and must respect DND preferences. See our transactional vs promotional SMS guide for more details on these categories.

Data Retention Requirements

The DPDP Act requires that personal data be retained only as long as necessary to fulfill the purpose for which it was collected. For OTP-related data, here are practical guidelines:

OTP Codes

OTP codes should be deleted or invalidated as soon as they are verified or expired. There is no reason to retain an OTP code after it has served its purpose. Best practice is:

• Set a short expiry window (5–10 minutes)
• Delete or invalidate the OTP immediately after successful verification
• Store only hashed versions during the active period
• Purge expired OTPs from your database regularly

Phone Numbers

If the phone number is part of the user's account, retention is justified for the duration of the account relationship. If the phone number was collected solely for a one-time verification (for example, verifying age or identity), it should be deleted once verification is complete.

Message Logs

Delivery logs (timestamps, delivery status, provider details) may be retained for operational and debugging purposes, but they should be anonymized or pseudonymized where possible. Avoid storing full phone numbers in logs; use hashed or truncated formats instead.

Cross-Border Data Transfer

The DPDP Act restricts the transfer of personal data outside India to countries that the Indian government has not specifically restricted. This is relevant for OTP implementations in several ways:

• SMS provider location — if your OTP provider routes messages through infrastructure outside India, phone numbers are technically transferred cross-border. Ensure your provider processes data within India or in approved jurisdictions.
• Cloud infrastructure — if your application stores phone numbers in a database hosted outside India, that constitutes cross-border transfer.
• Analytics and logging — if delivery logs containing phone numbers are sent to analytics services hosted abroad, that is also a transfer.

The government maintains and periodically updates a list of countries to which data transfer is restricted. As of now, the implementation rules are still being finalized, but the safest approach is to ensure all OTP-related data processing happens within India.

Compliance Checklist

Here is a practical checklist for ensuring your OTP implementation complies with the DPDP Act:

1. Privacy policy — include phone number collection and OTP processing in your privacy policy. State the purpose, retention period, and user rights.
2. Consent mechanism — ensure the OTP request flow constitutes valid consent (user-initiated, informed, unambiguous).
3. Purpose limitation — do not use phone numbers collected for OTP for marketing without separate consent.
4. Data minimization — collect only the phone number needed for verification. Do not require additional personal data solely for OTP delivery.
5. OTP hashing — store OTP codes as hashes (bcrypt or equivalent), never in plaintext.
6. Expiry and deletion — set OTP expiry (5–10 minutes) and delete codes after verification or expiry.
7. Secure transmission — use HTTPS for all API calls to your OTP provider. Never send phone numbers over unencrypted connections.
8. Access controls — limit who in your organization can access phone numbers and OTP logs.
9. Breach notification plan — have a plan to notify the Data Protection Board and affected users within 72 hours of a data breach.
10. Data processor agreement — ensure your OTP provider has a data processing agreement that covers DPDP Act obligations.
11. User rights — implement mechanisms for users to request access to, correction of, or deletion of their personal data.
12. Audit trail — maintain logs of consent and data processing activities for accountability.

StartMessaging and DPDP Compliance

When you use StartMessaging as your OTP provider, several DPDP compliance requirements are addressed by our infrastructure:

• OTP hashing — all OTP codes are bcrypt-hashed at creation. The plaintext code exists only in the SMS message itself.
• Automatic expiry — OTPs expire after the configured window and are automatically invalidated.
• India-based processing — all OTP processing and SMS routing happens through infrastructure within India.
• Secure API — all API communication is over HTTPS with SHA-256 hashed API key authentication.
• Minimal data retention — we retain only the data necessary for delivery verification and billing, with configurable retention periods.
• DLT compliance included — our DLT-free OTP delivery means you skip the entire DLT registration process while remaining fully compliant with TRAI regulations.

At Rs 0.25 per OTP, StartMessaging provides a compliant, secure, and affordable OTP solution. Get started without DLT registration, or review our API documentation and pricing.

Frequently Asked Questions