# How secure is Passbook?

Your family's financial information is personal. It includes your investments,
assets, insurance policies, important documents, and account credentials.



Before trusting an app with this data, you should know exactly how it is
protected.



Passbook is built around a simple principle: your financial data should remain
private, encrypted, and under your control.



Here is how that security architecture works in practice.


YOUR DATA IS ENCRYPTED ON YOUR DEVICE AND IN GOOGLE DRIVE

Passbook encrypts your financial database locally on your device before anything
leaves your machine. When your data syncs to your personal Google Drive, the
backup remains completely encrypted.




This means your financial information is never stored as readable text on your
computer or in Google Drive. Google stores only the encrypted backup file.


STRONG ENCRYPTION ALGORITHMS PROTECT YOUR INFORMATION

Passbook relies on established, peer-reviewed cryptographic standards rather
than proprietary methods:

 * Argon2id derives a cryptographic key from your Master Password. It is
   deliberately designed to be computationally expensive, protecting against
   brute-force password guessing even if an attacker obtains the encrypted file.
   
   

 * ChaCha20-Poly1305 encrypts your data and authenticates it simultaneously.
   Encryption keeps unauthorized parties from reading the contents, while
   authentication ensures any tampering or file corruption is immediately
   detected.


YOUR ENCRYPTION KEYS ARE PROTECTED BY HARDWARE SECURITY

Encryption is only as strong as the protection around its keys. Passbook uses
your device's native hardware security facilities to protect your encryption
keys.




On supported Macs, key storage uses Apple's Secure Enclave; on Windows, it uses
the Trusted Platform Module (TPM) alongside native operating-system keychains.



Your Master Password is never stored on Passbook's servers, and Passbook never
uploads your encryption keys to a central database.


PASSBOOK HAS NO CENTRAL DATABASE HOLDING YOUR FINANCIAL DATA

Passbook processes your financial information locally on your computer. It does
not maintain a central database of users' financial portfolios or asset records.



Your encrypted backup goes directly to your personal Google Drive. Your
financial portfolio data never passes through Passbook's servers—not even in
encrypted form.



Passbook's servers handle limited account and subscription details, but never
your financial records.



This architecture eliminates the risk of your data being exposed in a central
server breach.


SECURE READ-ONLY ACCESS IN THE BROWSER

You can access a read-only view of your financial records through the Passbook
web app without routing your portfolio through Passbook's servers.



The web app retrieves your encrypted backup directly from your Google Drive and
decrypts it locally inside your browser's memory using your Master Password.



The decrypted data remains isolated in your browser session and is completely
cleared when you sign out or close the tab.


MASTER PASSWORD AND ACCOUNT RECOVERY

Because Passbook operates without a central database, we do not store your
Master Password and cannot reset or retrieve it for you.



If you need to reset your password, you can do so using one of your active
devices through supported hardware authentication.



However, if you lose your Master Password and lose access to all your configured
devices, your encrypted backup cannot be recovered.


WHAT DOES THIS MEAN FOR YOU?

Passbook combines local encryption, hardware-backed key protection, and direct
Google Drive sync to deliver a zero-knowledge architecture where only you hold
the keys to your financial life.




While no software system can eliminate all external risks—such as malware on an
unpatched computer or compromised Google account credentials—Passbook's approach
ensures that a breach of our company servers will never compromise your
financial data.