If our server is breached
An attacker can obtain account metadata, request timing, ciphertext, and blob sizes. Note contents, titles, and folder names remain unreadable without your master key, which was never stored on the server.
Security
Umbra is designed so the service never receives the master key needed to open your vault.
How it works
When you set up Umbra, a random master key is generated on your device. Argon2id turns your passphrase into a separate wrapping key that protects the master key. Neither the passphrase nor plaintext master key travels to us. Everything you write is encrypted before it leaves the device, so the server receives ciphertext it cannot read.
The server sees
Only you see
Threat model
An attacker can obtain account metadata, request timing, ciphertext, and blob sizes. Note contents, titles, and folder names remain unreadable without your master key, which was never stored on the server.
You unlock your vault with your recovery key. Without either the passphrase or the recovery key, your data is unrecoverable — even by us. That's the honest tradeoff of true zero-knowledge: nobody holds a backdoor, including the people who built it.
Assurance status
The release candidate has crypto tamper tests, randomized multi-device reconciliation tests, tenant-isolation tests, zero-knowledge disk scans, dependency scanning, and backup/restore drills. It has not yet completed the independent security review required for hosted launch. We will link the public review summary here when that work is complete.
Recovery key
Your recovery key is a long, random string generated at setup. It's the one way back into your vault if you ever lose your passphrase. Because we can't reset a key we never had, we can't email it to you or regenerate it — write it down, store it in a password manager, or print it and put it somewhere physical. Treat it like the key to your house, because that's exactly what it is.