Privacy Policy & Security Specification
Nummo is an offline personal finance ledger engineered on a strict zero-ingestion premise: your financial transactions, balance sheets, categories, and cryptographic credentials reside exclusively in your physical device memory.
01. Core Architecture & Privacy Philosophy
Nummo ("the Software", "the App", or "the Service"), engineered and published by K Rajtilak, is an autonomous, standalone personal accounting ledger and mathematical budget tool.
Traditional personal finance applications frequently mandate remote account creation, scrape device SMS inboxes, harvest contact books, connect directly to open-banking APIs, or continuously upload ledgers to multi-tenant cloud databases. Nummo rejects this paradigm entirely. It operates as a closed-circuit, client-side offline appliance.
Architectural Guarantee: Nummo does not maintain backend servers, cloud databases, user authentication pipelines, or analytics endpoints. We do not possess the technical means to collect, view, decrypt, monetize, or transmit your financial ledger.
02. Data Classification Matrix
| Classification | Data Attributes | Collection Status | Storage Boundary | Network Egress |
|---|---|---|---|---|
| Personal Identifiers (PII) | Name, email, phone number, address, IMEI | Not Collected | None (Never requested) | 0 Bytes |
| Financial Transactions | Credits, debits, notes, timestamps, categories, balances | Local Only | Internal sandbox (EncryptedSharedPreferences) |
0 Bytes |
| Banking / Cards | Bank account numbers, cards, UPI IDs, PINs, OTP codes | Never Accessed | None (No banking integration) | 0 Bytes |
| SMS / Messages | SMS messages, notifications, call history, contacts | Prohibited | None (Permissions rejected) | 0 Bytes |
| Biometrics & PIN | 4-digit PIN hash, biometric authentication state | Local Only | Hardware Keystore / Titan Security Module | 0 Bytes |
| Analytics & Tracking | Crash dumps, telemetry, ad IDs, session traces | Not Collected | None (Zero tracking SDKs) | 0 Bytes |
03. On-Device Storage & Cryptography
- Operating System Sandboxing: On Android, data is persisted to the private application filesystem (
/data/user/0/com.nummo.app/). Inter-process isolation enforced by the Linux kernel prevents other apps from reading or modifying this storage. - Cryptographic PIN Storage: If you configure a security PIN, it is salted with high-entropy random bytes and hashed via
SHA-256/PBKDF2before persistence. The plaintext PIN is never stored. - OS Cloud Auto-Backup Exclusion: Nummo explicitly enforces
android:allowBackup="false"andandroid:fullBackupContent="false"in its manifest, prohibiting unencrypted cloud backups. - On-Device Report Generation: Document exports (JSON, CSV, PDF, Excel) are synthesized 100% in-memory using client-side routines and written strictly via Android's Storage Access Framework (SAF).
04. Permissions Audit
| Permission Identifier | API Scope | Technical Justification |
|---|---|---|
USE_BIOMETRIC / USE_FINGERPRINT |
Hardware Authentication | Invokes native biometric unlock dialog if App Lock is enabled. |
Storage Access Framework (SAF) |
System File Broker | Exports or imports local backup files chosen by the user. |
Prohibited Permissions
Nummo omits all invasive permissions: READ_SMS, RECEIVE_SMS, READ_CONTACTS, READ_CALL_LOG, ACCESS_FINE_LOCATION, CAMERA, RECORD_AUDIO, and Advertising ID tracking.
05. Google Play Financial Disclosures
- Non-Lending Declaration: Nummo is an offline bookkeeping and mathematical expense calculation utility. Nummo is not a lender, credit broker, loan facilitator, or financing platform. It does not issue, disburse, market, or broker loans.
- Non-Banking Declaration: Nummo is not a bank, NBFC, depository institution, or payment processor. It does not hold custodial funds or process electronic fund transfers.
- No Credit Scoring: Nummo does not calculate credit scores or transmit data to credit reporting agencies.
06. Statutory Frameworks
- GDPR (EU & UK): Fully compliant with Data Minimization (Art. 5(1)(c)), Right to Erasure (Art. 17), and Data Portability (Art. 20).
- CCPA / CPRA (California): Zero sale, sharing, or profiling of personal data.
- DPDP Act 2023 (India): Full digital sovereignty. No user data is ingested by external servers.
- Children's Privacy (COPPA): Zero data collection applies universally across all age groups.
07. Data Lifecycle & Erasure
- In-App Purge: Execute a complete, irreversible wipe of all records via
Settings → Danger Zone → Reset All Local Data. - OS Storage Reset: Clear data anytime via
Android Settings → Apps → Nummo → Storage → Clear Data. - Uninstall: Deleting the app instantly destroys the local sandbox and all stored records.
08. Engineering Attestation & Contact
I, K Rajtilak, engineer and creator of Nummo, attest that this Privacy Policy accurately represents the architectural operation of the Nummo application.
- Developer: K Rajtilak
- Developer Website: krajtilak.in
- Source Code: github.com/rajtilak-2020/Nummo
- Issue Tracker: github.com/rajtilak-2020/Nummo/issues