Zero-Knowledge-Platform/SECURITY_NOTES.md

Security Notes

Zero-Knowledge Guarantees

• Encryption and decryption happen only in the browser with the Web Crypto API.
• The backend only stores opaque iv + ciphertext blobs plus metadata.
• The backend never receives the plaintext data content for parent or child records.
• The backend never receives the encryption key.
• Password-derived auth material is separate from password-derived encryption material.
• The auth branch uses saltAuth and the encryption branch uses saltEnc.
• Parent deletion cascades to children using a backend transaction that still only handles encrypted blobs.
• No password reset or account recovery flow exists.

Backend Safety Checks

• No application logger or print() statements emit plaintext, password material, or derived keys.
• API responses avoid plaintext content and do not echo secrets.
• JWT expiry is enforced with ACCESS_TOKEN_EXPIRE_MINUTES.
• There is no refresh-token flow, so refresh handling cannot expose content.
• Ownership is derived from the JWT sub claim, not from client-supplied owner IDs.
• Content queries are scoped by ownerId and parentId only.

Operational Limits

• Full zero-knowledge security depends on the browser/client device being trusted.
• Server-side search over decrypted content is intentionally unsupported.
• Server-side content indexing is intentionally unsupported.
• If a user forgets their password, encrypted data is permanently unrecoverable.
• Production MongoDB should use a least-privilege app user, not an admin account.
• Production deployments should keep secrets out of source control and rotate JWT secrets on a policy schedule.

Notes

• The current development setup uses a local MongoDB service for convenience.
• The frontend keeps the encryption key only in React memory for the active session.
• Any future feature should be checked against the rule: does the server need plaintext? If yes, redesign it to run client-side.