Technical Documentation

Security Whitepaper

A complete technical overview of how Inventry protects your data using zero-knowledge, end-to-end encryption.

Last updated: January 2026 · v2.0

Contents

  1. 1. Overview
  2. 2. Zero-Knowledge Architecture
  3. 3. Encryption Specification
  4. 4. Master Key Architecture
  5. 5. Vault Sharing
  6. 6. Data Storage
  7. 7. Recovery Key (Critical)
  8. 8. Libraries & Standards

1Overview

Inventry is built on a zero-knowledge security model. This means:

  • ✓Your asset data is encrypted on your device before it ever leaves your phone.
  • ✓Inventry's servers never see your unencrypted data.
  • ✓Even if our database is breached, attackers get indecipherable ciphertext.
  • ✓We cannot comply with data requests for your asset details—we don't have them.

⚠️ Critical: No Email-Only Recovery

Because we use true zero-knowledge encryption, we cannot recover your data if you lose both your password AND your Recovery Key. Email-based "forgot password" resets require your Recovery Key to restore access to encrypted data. Save your Recovery Key in a safe place.

2Zero-Knowledge Architecture

Your Device
Encryption happens here
AES-256 + HMAC
Inventry Servers
Sees only ciphertext

Your Master Key never leaves your device. Our servers store only encrypted blobs and a "wrapped" (encrypted) copy of your Master Key that only you can unlock.

3Encryption Specification

Algorithm:       AES-256 (Advanced Encryption Standard)
Mode:            CBC (Cipher Block Chaining)
Padding:         PKCS7
Key Size:        256 bits
IV:              128-bit random IV per encryption operation

Integrity:       HMAC-SHA256 (Encrypt-then-MAC)
Key Separation:  Distinct keys for encryption vs. authentication
Format:          IV:Ciphertext:HMAC

✓ Authenticated Encryption (Encrypt-then-MAC)

Every piece of encrypted data includes an HMAC integrity tag. This prevents tampering attacks—if anyone modifies the ciphertext, decryption will fail rather than produce corrupted data. We use key separation: the encryption key and MAC key are derived separately, following cryptographic best practices.

AES-256 is the gold standard for symmetric encryption. It's the same algorithm used by:

    US Government
    Top Secret data
    Signal
    Messaging
    1Password
    Password vaults
    ProtonMail
    Email

4Master Key Architecture

Inventry uses a key-wrapping architecture similar to 1Password. Your password doesn't directly encrypt your data—instead, it unlocks a Master Key that does the actual encryption.

Your Password
→
PBKDF2
150,000 iterations
→
Wrapping Key
(KEK)
↓
unwraps
(stored encrypted on server)
→
Master Key
(DEK - random 256-bit)
→
Your Data
Assets, Photos
Key Derivation:   PBKDF2-SHA256
Iterations:       150,000 (production)
Salt:             SHA256(userId) - unique per user
Wrapping Key:     256-bit (encrypts Master Key)
Master Key:       256-bit random (encrypts all data)

// Password change is fast:
// Only re-wrap Master Key with new Wrapping Key
// No need to re-encrypt all your data

Why Key Wrapping?

Password changes are instant. When you change your password, we only re-wrap the Master Key with your new Wrapping Key. We don't need to re-encrypt gigabytes of photos and assets. This is the same architecture used by 1Password and other security-focused apps.

5Vault Sharing

When you share a vault with a family member, we use a Secure Invite Token system to transfer the Vault Key without exposing it to our servers.

1

Generate Invite

Your app generates a random Share Token (256-bit). This token is displayed as a code or QR.

2

Wrap Vault Key

A Share Wrapping Key is derived using PBKDF2(recipientEmail + shareToken). The Vault Key is encrypted with this, plus an HMAC for integrity.

3

Recipient Accepts

Your spouse enters the Share Token. Their app derives the same Share Wrapping Key (using their email + the token), unwraps the Vault Key, and stores it encrypted with their Master Key.

// Vault Sharing Flow
ShareToken = random(256 bits)
ShareKey = PBKDF2(recipientEmail + shareToken, salt, 150000)

// Owner encrypts:
WrappedVaultKey = AES(VaultKey, ShareKey)
HMAC = HMAC-SHA256(WrappedVaultKey, ShareKey)
Store: { wrapped_key, hmac, share_token_hash }

// Recipient derives same ShareKey, verifies HMAC, unwraps VaultKey

Server Never Sees Vault Key

The Share Token is exchanged out-of-band (shown on your screen, entered on theirs). Our server stores only the hash of the token for lookup, not the token itself. Without the token, the encrypted Vault Key is useless.

6Data Storage

● What's Encrypted

  • • Asset titles & descriptions
  • • Serial numbers & VINs
  • • Purchase prices & dates
  • • Notes & custom fields
  • • Photos (encrypted blobs)
  • • Receipt images

● What's NOT Encrypted

  • • Your email address
  • • Subscription status
  • • Category labels (for filtering)
  • • Timestamps (for sync)
  • • Wrapped Master Key (encrypted)

Photo Encryption

Photos are encrypted using keys derived from your Master Key with domain separation:

PhotoEncKey = HKDF(MasterKey, "photo-enc")
PhotoMacKey = HKDF(MasterKey, "photo-mac")
EncryptedPhoto = IV + AES(Photo, PhotoEncKey) + HMAC(ciphertext, PhotoMacKey)

📱 On-Device Viewing

When you view photos in the app, they are decrypted on your device and cached in the app's private sandbox for faster access and offline viewing. This cache is protected by your device's operating system security (iOS App Sandbox / Android App Sandbox) and is deleted when you uninstall the app. Photos are always encrypted in transit and at rest on our servers—we never see your unencrypted photos.

7Recovery Key (Critical)

⚠️ Read This Carefully

Your Recovery Key (format: INVT-XXXX-XXXX-XXXX-XXXX-XXXX-XXXX-XXXX) is the only way to restore access to your encrypted data if you forget your password.

If you lose both your password AND your Recovery Key, your data is permanently lost. We cannot help you.

✓ Change Password (Logged In)

If you're logged in and want a new password:

  1. Enter your current password
  2. Your Master Key is unwrapped
  3. Master Key is re-wrapped with new password
  4. Done—no data re-encryption needed

⚠️ Forgot Password

If you forgot your password, you must have your Recovery Key:

  1. Reset your Supabase auth password via email
  2. Enter your Recovery Key in the app
  3. Recovery Key unwraps your Master Key
  4. Master Key is re-wrapped with new password

How Recovery Key Works

When you create your account, Inventry generates both a Password-Wrapped Master Key and aRecovery-Wrapped Master Key. These are two separate "copies" of your Master Key, each wrapped with a different secret.

MasterKey = random(256 bits)

// Two ways to unwrap the same Master Key:
PasswordWrappedKey = AES(MasterKey, PBKDF2(password, userId))
RecoveryWrappedKey = AES(MasterKey, PBKDF2(recoveryKey, "recovery:" + userId))

// Both are stored on server. Either one can unwrap MasterKey.
Recovery Kit
Print and store in your safe

The app provides a "Recovery Kit" you can print. It contains your email and Recovery Key. Store it in a physical safe, safety deposit box, or with your estate documents. Do not store it digitally.

8Libraries & Standards

We use industry-standard, well-audited libraries. We do not implement our own cryptographic primitives.

LibraryPurpose
crypto-jsAES-256-CBC, PBKDF2-SHA256, HMAC-SHA256
expo-cryptoCryptographically secure random number generation (CSPRNG)
expo-secure-storeiOS Keychain / Android Keystore for local key storage

Randomness

All cryptographic random values (Master Key, IVs, Share Tokens) are generated usingexpo-crypto, which uses the platform's native CSPRNG (SecRandomCopyBytes on iOS, SecureRandom on Android). In development builds without native modules, the app will refuse to generate keys rather than fall back to insecure randomness.

Questions? Contact Support
Privacy PolicyTerms of Service