How backup encryption works
The short version: your files are encrypted on your phone, stored only on your own computer, and the encryption key and the encrypted data are never held by the same party. Here's the whole design, plainly.
Encryption happens on your phone
Each file is encrypted with AES-256-GCM before upload — contents and filenames both. What leaves your phone is ciphertext. (For the curious: each file gets its own data-encryption key, derived from the file's content and wrapped with your master key — which also lets your phone skip files that are already backed up without re-uploading them.)
What your storage computer holds
Encrypted files only. The storage computer never has your encryption key — decryption only ever happens on your phones. Someone who steals the machine, or a second computer that replicates your backups, sees only encrypted data.
Where your key lives
A 256-bit master key is generated on your phone the first time you back up. It's stored with your HostAnywhere account, so a new phone can restore with a simple sign-in — the same recovery model as iCloud — and it's cached in iCloud Keychain (iOS) and Android Keystore-backed storage (Android) for offline use.
Can HostAnywhere read my backups?
No — and here's the precise reason. Our servers hold your key but never your files; your computer holds your files but never the key. Keys and data are never in the same place, so a breach of our infrastructure alone exposes no content, and a stolen storage computer exposes none either. The only place both ever meet is your own phone.
What we can see
A one-way hash of each file (so your phone can skip files that are already backed up), storage usage totals, and which of your devices synced and when. Never contents, never filenames.
Restore
Sign in on the new phone → your key returns to it → your encrypted files flow back from your computer → decryption happens on the phone.
Deleting your data
Backup files are yours, on your machine — delete them anytime. Deleting your HostAnywhere account removes your key and your records from our side.
On the roadmap
An optional advanced mode where you hold the only copy of your key (via a recovery code) and HostAnywhere stores nothing. The trade-off is real — lose the code and your devices, and no one can recover your backups, including us. If that mode matters for your threat model, tell us — demand moves it up the list.
Questions about this design? We answer them — contact us. See also the privacy policy and the Storage Server & Backups documentation.