Privacy Policy for SignLock

1. Introduction

NexBrothers ("we," "us," or "our") respects your privacy and is committed to protecting the personal data of our users ("you" or "user"). This Privacy Policy explains how we collect, use, store, process, share, and protect your information when you use:

1. The SignLock: Signature App Lock mobile application for Android ("App" or "Application"), including all sub-features such as Signature Lock, Backup PIN, Drawing Privacy Mode, Custom Wallpapers & Themes, App Locking Schedules, and Guardian Remote Lock Control.
2. The official NexBrothers website located at https://www.nexbrothers.com ("Website").

This Privacy Policy is designed to comply with:

• Google Play User Data Policy
• Google Play Developer Program Policies
• Google Play Data Safety Requirements
• Google Play Accessibility API Policy
• Google Play Permissions Policy
• Google Play Advertising Policy
• General Data Protection Regulation (GDPR)
• California Consumer Privacy Act as amended by the California Privacy Rights Act (CCPA/CPRA)
• Other applicable international data protection laws

Please read this document carefully to understand our privacy practices. By installing, accessing, or using SignLock or our Website, you agree to the collection and use of information in accordance with this policy. If you do not agree with any part of this policy, please do not install or use the Application or Website.

2. Core Privacy Philosophy: Offline-First & Privacy-By-Design

SignLock is engineered with an offline-first, privacy-by-design architecture:

• Local Authentication & Security: Your signature gesture patterns, backup PIN numbers, application lock lists, and personal settings are stored exclusively on your device, protected by hardware-backed cryptographic encryption (AES-256-GCM via the Android Keystore).
• No Cloud Upload of Biometric/Gesture Passwords: Your signature coordinates and backup PINs are never uploaded to our servers, third-party clouds, or any remote infrastructure.
• End-to-End Encrypted Remote Features: Optional remote management capabilities (Guardian Remote Lock Control) utilize zero-knowledge, end-to-end encryption (E2EE) via ECDH key exchange. Remote policy updates are encrypted on-device before transmission, preventing anyone — including NexBrothers and Google — from viewing your policy content.

3. Information We Collect and How We Use It

A. Information Stored Locally on Your Device (Not Uploaded)

B. Information Processed for Remote Sync (Guardian Mode)

C. Technical & Diagnostic Information (Automated Collection)

D. Website Information Collection (nexbrothers.com)

When you visit our Website, we may collect:

• Cookies & Local Storage: Technical cookies required for website operation, layout performance, and user consent settings.
• Web Analytics: Anonymous visit metrics including browser type, operating system, referrer URL, pages visited, and general country location.
• Support Inquiries: If you contact us via email or web contact forms, we collect your name, email address, and the contents of your message solely to respond to your support request.

4. Detailed Audit of Android System Permissions

SignLock requests specific Android system permissions to execute its security features. Each permission is requested in accordance with Google Play Developer Policies and is used strictly for its declared purpose:

1. BIND_ACCESSIBILITY_SERVICE (Accessibility Service API)

• Declaration: Declared in AndroidManifest.xml under ScreenLockAccessibilityService.
• Purpose: Used exclusively to detect window state changes (TYPE_WINDOW_STATE_CHANGED and TYPE_WINDOW_CONTENT_CHANGED) to identify when a user opens an application that is marked as protected in SignLock.
• User Privacy & Data Safety Protection:
  • Zero Keystroke Logging: SignLock's Accessibility Service does NOT monitor, log, capture, or transmit typed text, passwords, search queries, or form inputs.
  • Zero Content Interception: It does NOT read on-screen text, message contents, emails, or personal data inside other applications.
  • Zero Remote Transmission: Foreground application detection is evaluated 100% locally on the device against local database rules.
  • User Authorization: The service must be explicitly enabled by the user in Android System Settings and can be revoked at any time.

2. QUERY_ALL_PACKAGES

• Declaration: Declared in AndroidManifest.xml.
• Purpose: On Android 11+ (API level 30+), SignLock requires this permission to query the list of installed applications on your device. This allows SignLock to present a full list of installed apps in the App Selection dashboard so you can select which apps to lock.
• Privacy Assurance: Installed package lists are processed strictly on-device and are never uploaded to any remote server, database, or third party.

3. SYSTEM_ALERT_WINDOW ("Display Over Other Apps")

• Purpose: Enables SignLock to overlay the secure signature unlock screen immediately on top of a protected application when launched, blocking unauthorized access until the correct signature or PIN is entered.

4. CAMERA

• Purpose: Used exclusively during Guardian pairing mode. Uses CameraX and Google ML Kit Barcode Scanning to scan the QR code displayed on a paired device.
• Privacy Assurance: The camera preview is analyzed in real time in device RAM to extract the QR code payload. No video, photography, or image files are recorded, saved, or uploaded.

5. POST_NOTIFICATIONS

• Purpose: On Android 13+ (API level 33+), allows SignLock to display persistent protection status notifications (ensuring the background service is not killed by the OS) and security alerts (such as lockout warnings or Guardian policy updates).

6. RECEIVE_BOOT_COMPLETED

• Purpose: Ensures SignLock's background protection service automatically resumes monitoring immediately after your device reboots.

7. SCHEDULE_EXACT_ALARM

• Purpose: Triggers time-precise locking schedule transitions configured by the user (e.g., automatically locking financial apps at midnight).

8. REQUEST_IGNORE_BATTERY_OPTIMIZATIONS

• Purpose: Prompts the user to exclude SignLock from aggressive OS battery saver limits so background protection remains active and uninterrupted.

9. MODIFY_AUDIO_SETTINGS

• Purpose: Controls audio playback for optional unlock sound effects and silent feedback during signature drawing.

10. com.google.android.gms.permission.AD_ID (Google Advertising ID)

• Purpose: Used by the Google Mobile Ads (AdMob) SDK on Android 13+ to provide ad delivery, frequency capping, and anti-fraud detection for free-tier users.

11. WorkManager Background Processing Tasks

• EntitlementSyncWorker: Periodically executed in the background (every 6 hours) to re-verify Google Play Store billing entitlement tokens and ensure active subscription states are updated locally.
• PolicyCatchUpWorker: Executed in Guardian mode to retrieve pending end-to-end encrypted policy rules from Firebase Cloud Firestore when network connectivity is restored.

12. Broadcast Receivers

• BootCompletedReceiver: Receives android.intent.action.BOOT_COMPLETED to re-initialize protection services upon device restart.
• ProtectionAlarmReceiver: Receives exact alarm triggers from SCHEDULE_EXACT_ALARM to activate or deactivate app locking schedules.
• PackageInstallReceiver: Receives android.intent.action.PACKAGE_ADDED when a new app is installed on the device so SignLock / Guardian can evaluate and apply protection rules to the newly installed application.

5. Third-Party SDKs and Data Processors

SignLock integrates with a minimal set of trusted third-party SDKs to provide core app functionality, analytics, billing, and advertising. Each third-party processor handles data according to their respective privacy policies:

6. How Information Is Processed and Retained

A. Processing Location

• On-Device Processing: All signature vector comparisons, PIN hashing, accessibility window checks, schedule calculations, wallpaper caching, and database queries occur entirely on your Android device.
• Remote Cloud Processing: Remote cloud infrastructure (Google Firebase / Firestore) is used solely to pass encrypted Guardian sync messages between paired devices and to manage anonymous remote configuration flags.

B. Data Retention Period

• Local Application Data: Signature templates, backup PINs, protected app lists, and preferences remain stored on your device until you manually clear them via the in-app "Reset" option or uninstall the Application.
• Guardian Firestore Sync Documents: Encrypted sync pairing documents stored in Firebase Firestore are deleted upon unpairing or after 30 days of inactivity.
• Crash & Diagnostic Logs: Crash reporting logs sent to Sentry and Firebase Crashlytics are automatically deleted after 90 days.
• Analytics Data: Aggregated, non-personally identifiable analytics data stored by Google Firebase Analytics is retained for up to 14 months.

7. User Data Control, Rights, and Deletion Procedures

We empower users with complete control over their personal data. Depending on your jurisdiction (including the EU/EEA under GDPR and California under CCPA/CPRA), you have specific data rights:

A. How to Delete Your Data Immediately

1. In-App Data Reset (Complete Instant Erasure): Open SignLock → Settings → Security → Reset App. Confirm reset. This permanently deletes all signature templates, backup PINs, protected app lists, lockout history, and local preferences from device storage and wipes encryption keys from the Android Keystore.
2. Guardian Unpairing (Remote Sync Erasure): Open SignLock → Guardian tab → Unpair Device. This instantly revokes cryptographic keys and deletes the associated pairing document from Firebase Cloud Firestore.
3. App Uninstallation: Uninstalling SignLock from your Android device immediately destroys all application files, Room databases, DataStore preferences, and private storage directories.

B. Rights Under GDPR (European Economic Area & UK Users)

If you reside in the EEA or UK, you hold the following rights regarding your personal data:

• Right of Access: You have the right to request information about the personal data we process.
• Right to Erasure ("Right to be Forgotten"): You have the right to request the deletion of your personal data.
• Right to Data Portability: You have the right to receive a copy of your personal data in a structured, machine-readable format.
• Right to Restrict or Object to Processing: You may object to or restrict processing of your data, including direct marketing or ad personalization.
• Right to Withdraw Consent: Where processing is based on consent, you may withdraw your consent at any time without affecting lawful processing prior to withdrawal.

To exercise any of these rights, contact us at nexbrotherss@gmail.com.

C. Rights Under CCPA / CPRA (California Residents)

California law grants residents specific rights:

• Right to Know / Access: Request disclosure of categories and specific pieces of personal information collected.
• Right to Delete: Request deletion of personal information collected from you.
• Right to Opt-Out of Sale or Sharing: SignLock does NOT sell your personal information or share it for cross-context behavioral advertising.
• Right to Non-Discrimination: We will not discriminate against you for exercising your CCPA/CPRA rights.

8. Security Measures & Encryption Protocols

NexBrothers implements industry-leading security practices to safeguard your data against unauthorized access, alteration, disclosure, or destruction:

• Hardware-Backed Encryption: All sensitive local data (signature gesture matrices and backup PINs) are encrypted using AES-256-GCM keys generated via the Android Keystore system.
• End-to-End Encrypted Cloud Sync: Guardian pairing uses Elliptic-Curve Diffie-Hellman (ECDH) key exchange and AES-256-GCM payload encryption. Remote policies cannot be decrypted by intermediate servers.
• Timing-Attack Protection: PIN validation uses constant-time string comparison (MessageDigest.isEqual) to prevent cryptographic timing side-channel attacks.
• Clock-Tampering Protection: Lockout timers utilize system monotonic clocks (SystemClock.elapsedRealtime) to prevent users or unauthorized actors from bypassing lockouts by altering device system time.
• PII Suppression in Crash Reports: Release builds are configured with send-default-pii=false and attach-screenshot=false to ensure no sensitive screen contents or personal identifiers enter crash stack traces.

9. Children's Privacy

SignLock is a general audience tool and parental control utility. The Application is not directed to children under the age of 13 (or under 16 in the European Union). We do not knowingly collect personal identifiable information from children.

When SignLock is used in Guardian Mode for parental supervision, the pairing process and policy controls must be configured and managed by a parent or legal guardian. If you believe a child has provided us with personal information without parental consent, please contact us at nexbrotherss@gmail.com, and we will immediately take steps to remove such information.

10. International Data Transfers

Our Application is designed to operate primarily on your local device. Where cloud infrastructure is used (such as Google Firebase for Guardian sync, Google AdMob, or Sentry), your data may be transferred to and processed on servers located outside your state, province, or country (including in the United States).

These third-party providers comply with recognized international transfer mechanisms, including the EU-U.S. Data Privacy Framework, Standard Contractual Clauses (SCCs), and robust encryption standards to protect your data across borders.

11. Website Cookies and Tracking Technologies

When you interact with our Website (https://www.nexbrothers.com), we use standard web tracking technologies:

• Essential Cookies: Necessary for basic website navigation and access to secure areas.
• Analytical Cookies: Help us understand site visitor counts, traffic sources, and popular pages.
• Cookie Management: You can instruct your web browser to refuse all cookies or to indicate when a cookie is being sent. However, some website features may not function properly without cookies.

12. Advertising and Subscriptions

A. Free Version & Advertisements

The free version of SignLock displays advertisements provided by Google Mobile Ads (AdMob). AdMob may use your device's Advertising ID (AD_ID) and coarse location to serve contextual or personalized ads, subject to your device ad tracking settings and consent. You can reset or limit ad tracking in your Android device settings under Settings → Google → Ads.

B. Premium Subscription & Purchases

Upgrading to SignLock Premium removes all advertisements and unlocks advanced Guardian and personalization features. Subscription transactions are processed directly by Google Play Billing. NexBrothers does not collect or store your credit card details, bank account numbers, or payment credentials.

13. Changes to This Privacy Policy

We may update our Privacy Policy from time to time to reflect changes in our application features, legal requirements, or operational practices. When we make material changes, we will:

1. Update the "Last Updated" date at the top of this Privacy Policy.
2. Post the revised Privacy Policy on our Website at https://signlock.nexbrothers.com/privacy-policy.
3. Provide an in-app notice or notification where appropriate.

We encourage you to review this Privacy Policy periodically to stay informed about how we protect your privacy.

14. Contact Us & Data Protection Officer

If you have any questions, concerns, feedback, or data privacy requests regarding this Privacy Policy or our practices, please contact us at: