> ## Documentation Index
> Fetch the complete documentation index at: https://support.tuckthis.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Encryption model

> Technical details for how Tuck seals and unwraps vault data.

Tuck uses a random 256-bit data-encryption key (DEK) for the vault.

## Vault data

Titles, bodies, tag names, attachment bytes, and todo titles are encrypted with AES-256-GCM.

## Passphrase wrap

The vault passphrase is stretched with PBKDF2-HMAC-SHA256 using 600,000 iterations and a 16-byte salt, then used to wrap the DEK.

## Recovery wrap

The Recovery Kit independently wraps the same DEK so recovery does not require the normal passphrase.

## Client compatibility

The web and native Apple clients must use the same wrap format and snapshot shape. The iOS implementation intentionally follows the web vault contract instead of inventing a second crypto format.

<Warning>Changes to the vault format are cross-platform compatibility changes. Treat them like a protocol migration, not a local implementation detail.</Warning>