Encryption, keys, and security
ShieldFive encrypts your files in your browser with a post-quantum hybrid suite before they reach our servers. Unwrapped encryption keys are handled in your browser, while wrapped key material can be stored for sync and recovery workflows.
How are encryption keys created?
At signup, your browser generates a random 256-bit vault key. That vault key is wrapped under two independent wrapping keys: one derived from your master password with Argon2id, and one derived from a random 32-byte recovery key shown to you once. Either path unwraps the same vault key. Every file you upload then gets its own random encryption key, which is wrapped under the vault key. If you protect a share link with a share password, the file key is additionally wrapped for that share.
What encryption algorithm does ShieldFive use?
ShieldFive seals new files with a post-quantum hybrid suite: ML-KEM-1024 (NIST FIPS 203) combined with XChaCha20-Poly1305 via an HKDF-SHA-256 combiner. Files are encrypted in chunks for large uploads; the chunk size is stored with each file so it can be decrypted safely. Files uploaded before May 2026 used AES-256-GCM and remain readable.
How does ShieldFive verify my encrypted files?
Each upload part includes a checksum verified by storage, and ShieldFive verifies the final stored size before marking an upload complete. If ciphertext is corrupted or tampered with, the suite's authenticated encryption causes decryption to fail on the client.
Is my encrypted data protected from tampering?
Yes. The encryption suite provides authenticated encryption, so any modification causes decryption to fail. This protects you from corrupted or maliciously modified files.
How are filenames and folder names encrypted?
File and folder names are encrypted in your browser under your vault key before being sent to ShieldFive's servers. This means:
- File and folder names are encrypted on your device; we store only the ciphertext
- Names are encrypted with the same strong encryption as file contents
You can browse and search your files by name while your vault is unlocked. Because names are encrypted, search runs on your device and covers names in your open session only, not file contents
The server stores only encrypted names that look like random data.
Where is my vault key stored?
Your unwrapped vault key stays in memory while you use ShieldFive. The wrapped vault key is stored with your account so that you can unlock it from any session by signing in.
- Unwrapped key stays in memory on your device
- The wrapped vault key is stored server-side
- Cleared from memory when you close the tab or sign out
You'll be prompted to re-enter your master password when needed.
What are passphrase hints and are they secure?
When sharing files, you can optionally add a passphrase hint to help recipients remember the correct passphrase. Hints are encrypted in your browser before being stored, so they're only visible to people who successfully decrypt the shared file. Never put the actual passphrase in the hint.
Can I change my master password?
Yes. Changing the master password re-derives the wrapping key with Argon2id and re-wraps your vault key under it; the underlying vault key and every per-file key stay the same, so existing files don't need to be re-encrypted. Per-file content keys themselves are permanent for a given file.