Briefcase encrypts your files on-device before they ever leave. Connect your own Google Drive accounts — we route your data, but we can never read it.
No trust required. Your data is locked before it leaves your hands.
Download on iOS or Android. Set a strong password — it never leaves your device.
Your password derives encryption keys via Argon2id. Only you can unlock your files.
Add as many Google accounts as you want. Each one adds 15 GB of storage you already own.
Files encrypt on-device, route through our server as ciphertext, and land in your Drive.
Files encrypt with XChaCha20-Poly1305 before upload. Each file gets its own random 256-bit key.
Files live in your Google Drive — not on a server you have to blindly trust.
Get started with Briefcase-provided storage — no account or credit card needed.
Connect as many Google accounts as you want. Each free account adds 15 GB of storage.
Our server routes encrypted bytes — mathematically incapable of reading your files.
Back up any file type — photos, documents, videos — seamlessly across iOS and Android.
Every cryptographic primitive Briefcase uses is documented, open, and battle-tested.
Algorithm Details
| Password → Master Key | Argon2id (RFC 9106) |
| Master Key → Keypair | X25519 seed keypair |
| Per-file key wrapping | crypto_box_seal |
| File encryption | XChaCha20-Poly1305 |
| KDF Memory | 64 MiB / attempt |
| KDF Iterations | 3 passes |
| Crypto library | libsodium |
| Server access | Ciphertext only |
Briefcase servers cannot read your files, names, or metadata — ever.
Each item has its own key. Compromising one affects nothing else.
Your password stays on your device. We have no reset mechanism because we have no access.
Argon2id makes brute-force attacks extremely slow — even with specialised GPU hardware.
XChaCha20-Poly1305 detects and rejects any tampering with ciphertext.