CellEncrypt

Password-Based Cell Encryption for Google Sheets™

🔒 PBKDF2 Encryption 🛡️ HMAC Integrity ⏱️ 6-Hour Sessions 🔑 Cell-Specific Keys 👁️ Viewer Protection

Before Encryption:

CellEncrypt Before Preview

After Encryption:

CellEncrypt After Preview

⚠️ IMPORTANT: Understanding Protection Scope

What CellEncrypt Protects:

  • ✓ Hides content from VIEWERS (read-only access)
  • ✓ Protects exported/downloaded spreadsheet copies
  • ✓ Secures current cell values in screenshots

Critical Limitation:

  • ⚠️ Users with EDITOR access can ALWAYS view edit history
  • ⚠️ Original unencrypted values visible in version history
  • ⚠️ Only grant editor access to fully trusted users
  • ⚠️ Only the spreadsheet OWNER can encrypt/decrypt cells

Recommendation: Use CellEncrypt for viewer privacy. This is protection designed for controlling who can see data in VIEW mode, not for securing data from editors.

Key Security Features

🔐

Password-Based Encryption

PBKDF2 key derivation with 10,000 rounds ensures strong password-based protection. No stored keys - only you know the password.

🆔

Cell-Specific Keys

Each cell gets a unique encryption key derived from your password plus a UUID. Same password, different keys per cell.

✓

HMAC Integrity Verification

Every encrypted cell includes an HMAC signature to detect tampering or incorrect passwords during decryption.

⏱️

Session Password Caching

Enter your password once and work for 6 hours. Cache automatically expires, or manually end session anytime.

📦

Batch Processing

Encrypt or decrypt up to 50 cells at once with progress tracking. Optimized for performance with large selections.

🧹

Orphan Data Cleanup

Built-in cleanup tool removes encrypted data for deleted cells, keeping your storage efficient and organized.

How CellEncrypt Works

Installation

  1. Open your Google Sheets™ document
  2. Navigate to Extensions → Add-ons → Get add-ons
  3. Search for "CellEncrypt"
  4. Click Install and authorize the required permissions
  5. Refresh your spreadsheet to see the CellEncrypt menu

🌐 View on Google Workspace Marketplace

Or visit directly: https://workspace.google.com/marketplace/app/cellencrypt/933661203390

Encrypting Cells (Owner Only)

  1. Select the cells containing sensitive data
  2. Click CellEncrypt → 🔒 Encrypt Selected Cells
  3. Read and accept the editor limitation warning (first-time only)
  4. Enter your encryption password (minimum 8 characters recommended)
  5. Password is cached for 6 hours for convenience
  6. Cells will display [ENCRYPTED] - original data stored securely

Decrypting Cells (Owner Only)

  1. Select cells showing [ENCRYPTED]
  2. Click CellEncrypt → 🔓 Decrypt Selected Cells
  3. If password cached, it's used automatically (or enter manually)
  4. Original cell values will be restored
  5. Encrypted data removed from storage automatically

🔑 Password Management

Critical: Your password is NOT stored permanently. If you forget your password, you can only recover clear text from change history.

Password Session Features:

  • Password cached for 6 HOURS after first entry
  • No need to re-enter during active session
  • Use 🚪 End Password Session to logout manually
  • Session expires automatically after 6 hours

Tips:

  • Use a strong, memorable password (8+ characters recommended)
  • Store your password securely (password manager)
  • Only spreadsheet owner can encrypt/decrypt cells

Storage & Account Limits

Feature Free Account Premium Account
Storage Limit 5 KB 500 KB
Estimated Cells ~100-200 cells ~10,000-20,000 cells
Password Sessions ✓ 6 hours ✓ 6 hours
Batch Processing ✓ 50 cells/batch ✓ 50 cells/batch
Cleanup Tools ✓ ✓
License Duration - 1 Year
Support Cost Free From $1 USD (one-time)

☕ Upgrade to Premium Account

Support CellEncrypt development with any amount starting from $1 USD (one-time payment) and unlock 100x more storage (500 KB) with a 1-year license!

☕ Support on Buy Me a Coffee

How it works:
1. Support with any amount ($1+) using your Google email
2. Wait 2-5 minutes for webhook processing
3. Get your license from bmc.numbrate.com
4. Activate in CellEncrypt → 🎫 Enter License Key
5. Enjoy 500 KB storage for 1 year!

Note: Storage is calculated based on encrypted data size. Actual cell count varies by content length. Use CellEncrypt → Show Storage Usage to monitor your usage. Premium status is verified through the webhook API connected to Buy Me a Coffee.

Technical Security Details

Encryption Implementation

Key Derivation

Algorithm: PBKDF2-like with SHA-256

Rounds: 10,000 iterations (master) + 100 (per-cell)

Salt: Unique per spreadsheet

Cell Keys: Master key + UUID per cell

Encryption Method

Cipher: Block-based stream cipher

IV: Random 16-byte initialization vector

Block Size: 32 bytes (SHA-256)

Format: V3:IV:Encrypted|HMAC|Signature

Data Integrity

Method: HMAC-SHA256

Verification: Constant-time comparison

Tampering: Detected before decryption

Version: V3 protocol identifier

Data Storage

Encrypted data is stored in Google Apps Script Properties (inaccessible to viewers). Cell metadata uses zero-width space prefixes to hide UUIDs in cell notes. All storage is within Google's infrastructure - no external servers.

Session Security

Password cached in CacheService (user-specific, 6-hour expiration). Session keys cleared after each operation. No persistent storage of passwords or derived keys. Only spreadsheet owner can perform encryption/decryption operations.

Frequently Asked Questions

How do I upgrade to Premium status?
Visit buymeacoffee.com/numbrate and support with any amount starting from $1 USD. Important: Use the same email address that you use with Google Sheets. After 2-5 minutes, retrieve your license key from bmc.numbrate.com and activate it in CellEncrypt → 🎫 Enter License Key. Your storage will increase from 5 KB to 500 KB for 1 year.
Can editors see my encrypted data?
Editors can see the current encrypted state (cells show [ENCRYPTED]), but NOT the original content - unless they check edit history. Important: Google Sheets version history will show all previous values including unencrypted data. Only share editor access with fully trusted users.
What happens if I forget my password?
Encrypted data can be only recovered from history without the correct password. CellEncrypt uses password-based encryption with no backup recovery mechanism. Always store your password securely in a password manager.
How long does the password session last?
Password sessions last 6 hours from the time you enter your password. During this time, you can encrypt/decrypt without re-entering the password. Use CellEncrypt → End Password Session to manually clear the cache earlier.
Is encrypted data stored on external servers?
No. All encrypted data is stored in Google Apps Script Properties within your spreadsheet. No data is transmitted to external servers. Everything stays within Google's infrastructure.
Can I encrypt cells with formulas?
CellEncrypt encrypts the current cell VALUE, not the formula. If you encrypt a cell containing a formula, the calculated result will be encrypted. When decrypted, you'll get the value back, not the original formula.
What happens to encrypted data when I delete a cell?
Deleting a cell leaves "orphaned" encrypted data in storage. Use CellEncrypt → Clean Up Orphaned Data to scan and remove encrypted data for deleted cells, freeing up storage space.
Can multiple users encrypt different cells with different passwords?
Only the spreadsheet owner (the person who first installed CellEncrypt) can encrypt/decrypt cells. This prevents conflicts and ensures consistent password management. Other users can view but not modify encrypted cells.
Does CellEncrypt work offline?
CellEncrypt requires an internet connection as it runs through Google Apps Script. All encryption/decryption happens server-side within Google's infrastructure for security and consistency.
How do I check my storage usage?
Click CellEncrypt → Show Storage Usage to see your current usage, percentage of limit, number of encrypted cells, and remaining space. You'll receive warnings when approaching 80% capacity.
Can I use different passwords for different cells?
Yes, Add-on does not store password anywhere centrally other then 6 hours temporary caching. So it is suggested to use same password always otherwise you should keep track of cell passwords with different UID's later to decrypt.

Professional Use Cases

HR & Payroll Data

Protect salary information, social security numbers, and performance reviews from viewers while maintaining spreadsheet collaboration with trusted HR staff.

Financial Planning

Secure account numbers, investment portfolios, and financial projections in shared planning spreadsheets with family or advisors.

Client Data Management

Encrypt client contact details, confidential notes, and pricing information in CRM spreadsheets shared with your team.

Research Data

Protect participant identifiers, survey responses, and confidential research data while collaborating with research teams.

Legal Documentation

Secure case details, client information, and settlement amounts in legal case management spreadsheets.

Healthcare Records

Protect patient identifiers, medical notes, and HIPAA-sensitive information in shared healthcare administration spreadsheets.

Technical Support

We're here to assist you

For questions, technical support, or feedback about CellEncrypt

Email: numbrate@gmail.com