Security architecture

Plain-language version. The full technical design document ships with the source.

The one-sentence version

Your 2FA secrets are encrypted on your device with keys only you hold — KeyNesta’s servers store ciphertext they cannot open, and generating codes never requires the internet at all.

How your vault is encrypted

When you create a vault, your device generates a random 256-bit master key. That key — never your passphrase directly — encrypts your vault with AES-256-GCM, an authenticated cipher that detects any tampering.

Your passphrase protects the master key: it is stretched with scrypt (a deliberately memory-hard function that makes GPU brute-force attacks expensive) and the result wraps the master key. Changing your passphrase re-wraps one small block; your data is never re-encrypted or exposed in the process.

Entering a wrong passphrase simply fails authentication. There is no hint, no partial decryption, no oracle.

Zero-knowledge sync

Sync is optional. When enabled, every object — each account entry, group, space — is individually encrypted with your master key before upload. The server sees opaque ciphertext plus the minimum it needs to sync: object IDs, version numbers, timestamps. It never sees secrets, code values, account names, notes, or your folder structure.

Your account password authenticates you to the sync service; it can’t decrypt anything. Your vault passphrase never leaves your devices. Signing in on a new device downloads ciphertext that only your passphrase can unwrap — locally.

On your devices

• iPhone & Android: the master key can be stored in the hardware-backed Keychain/Keystore behind Face ID or fingerprint. The vault locks when the app goes to the background.
• Web: the vault is stored encrypted in your browser; the master key exists only in memory while unlocked and is discarded on lock or after an inactivity timeout.
• Multiple vaults on one device are cryptographically independent — separate keys, separate passphrases, separate sync accounts.

What we deliberately do not do

• No invented cryptography — audited implementations of standard primitives (scrypt, AES-256-GCM, HMAC) only.
• No ads, no analytics SDKs harvesting behavior, no selling of any usage data. An authenticator sees your whole digital life; monetizing that is disqualifying.
• No lock-in: encrypted backups are portable files you own, and standard exports always work.
• No logging of secrets or generated codes, anywhere, ever.

Honest limits

Security claims without caveats are marketing. Here are ours:

• Your passphrase is the wall. Zero-knowledge also means we cannot reset it — a weak passphrase weakens everything, and a forgotten one without a backup means the vault stays sealed.
• A fully compromised device (malware, malicious browser extensions) can read what you can read while a vault is unlocked. Auto-lock narrows that window; it cannot eliminate it.
• Clipboard clearing after copying a code is best-effort — operating systems keep clipboard histories we cannot fully control.
• Independent third-party cryptographic review is on our roadmap and will be published; until then, treat “secure” as “well-designed and tested,” not “audited.”

Questions?

Write to security@keynesta.com — vulnerability reports are welcome and taken seriously.