Family Letter

Family Asset Registry
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Security Whitepaper

Family Letter Security & Encryption Whitepaper

No polished jargon, no runaround — plain words on where your data lives, how it is encrypted, and how to hand it over to your family safely.

1. Where your data goes and what "online" means (core facts)

From the very beginning, Family Letter was designed around a purely local storage principle. All recorded asset locations, access steps, letter pages, and attachments up to 20MB (PDF/images/text documents/spreadsheets) exist only on the user's phone.

Vault data never goes online and is never uploaded to any server. The only network use is Google Play Billing for in-app purchase and restoring purchases.

2. Two layers of protection (in plain words)

When you export a backup, Family Letter creates an encrypted .vault file (not the plain-text PDF common elsewhere). It is protected by AES-256 encryption and years of cryptography engineering:

1. AES-256 encryption
Seals every entry and attachment

Uses industry-standard AES-256 encryption. Without the correct master password, anyone who obtains the backup file sees only meaningless random noise.

2. Years of cryptography engineering
The password lives only in your head; a wrong password or a single changed byte blocks decryption

The password lives only in your head and is never stored anywhere. Years of refined cryptography engineering resist brute-force guessing; if the password is wrong, or the .vault file is altered by even one byte, the app immediately refuses to decrypt.

3. Best practices for family backup and handover

  1. Separate passwords from assets: Keep everyday login passwords in your phone's built-in password manager; in Family Letter, only record "what assets exist, where they are, and how to access them." Private keys and recovery phrases never enter the app.
  2. Keep the backup file and its password apart: After exporting an encrypted .vault backup in Pro, you can send it to family via social media / email or store it on a home USB drive; write the master password on paper and keep it in a physical drawer at home.
  3. Free import and restore: After your family downloads the Family Letter app for free, they can import the .vault backup with no limit on entries and view everything by entering the master password you left.