Introduction
Hardware-backed key custody — automatic, on your device.
Buzzio wraps identity secrets with AES-256-GCM using a key held by the platform keystore before they sit in flutter_secure_storage. That is hardware-backed key custody: the wrap key prefers StrongBox or the TEE on Android, and the Secure Enclave–backed Keychain path on capable iPhones.
We never receive your mnemonic or private messaging keys. This layer hardens how those secrets rest on the phone — it is not a server feature.
Why Buzzio is best for key custody
Wrap before rest
Secrets are AES-GCM wrapped before storage — not left as plain blobs in app storage.
StrongBox first on Android
Android prefers StrongBox, then falls back to TEE when StrongBox is unavailable.
Keychain on iOS
iOS uses Keychain AES with WhenUnlockedThisDeviceOnly, non-sync — tied to the device unlock hierarchy.
Automatic migration
Legacy installs migrate identity secrets to hardware wrap once on cold start — no marketing toggle required.
Honest claim language
We claim hardware-backed key custody — not that StrongBox signs every chat message.
Pairs with Lock Database
App lock’s Lock Database wraps the SQLCipher key while locked — a related seal for the local DB, separate from this identity wrap.
What you get
- AES-256-GCM wrap
- Android StrongBox / TEE
- iOS Keychain
- Mnemonic wrap
- Master & private keys
- Vault / backup keys
- Auto migration
- No server custody
How it works
Wrap model
Sensitive material is encrypted with AES-256-GCM under a platform hardware key, then stored. The on-disk format is a versioned blob (HW1. plus encoded nonce, ciphertext, and tag). At use time, the platform unwraps in the secure environment the device provides — Buzzio never uploads that wrap key.
Android and iOS
Android
- Android Keystore AES wrap
- Prefers StrongBox
- Falls back to TEE
iOS
- Keychain AES wrap
- WhenUnlockedThisDeviceOnly
- Non-sync; SE hierarchy on SE devices
On platforms without this wrap path, material may pass through without the extra hardware layer — phone builds are the focus.
What is wrapped
- 12-word mnemonic
- Master key and messaging private key material
- Vault and backup recovery keys held in secure storage
Protocol crypto such as secp256k1 ECDH / ECDSA for messaging still runs in software in the app. Hardware wrap is about how long-lived secrets rest — not a claim that every ratchet step is executed inside the Secure Enclave.
Boundaries
What hardware-backed keys do not mean
It is not “StrongBox signs every message.” It is not hardware ECDH for the whole protocol. It is not a user toggle you turn on for marketing. Compromised unlocked devices, malware with enough privilege, or a lost recovery phrase still defeat custody goals. Write your phrase offline — hardware wrap does not replace offline backup of the words.
Tips
- Keep device OS and Buzzio updated for keystore fixes
- Enable App lock + Lock Database for an extra seal on the local DB
- Never enter your phrase on web or in chat with “support”
- Treat a lost phrase as unrecoverable — hardware wrap cannot reset it
Custody without a slogan
Download Buzzio — hardware-backed wrap runs automatically on supported phones while your keys stay yours.