Fold is a public browser-only encryption tool. It is meant to protect message contents from anyone who does not have the recipient's private key, including people who receive, store, forward, or host the encrypted Fold package.
Fold protects
- Plaintext messages before they are copied out of the app, as long as the browser and device are trustworthy.
- Private keys and raw text from intentional app-side persistence. Fold does not intentionally save them in local storage, session storage, cookies, IndexedDB, or a backend.
- Popout sync traffic between the main window and its matching popout through a random private sync session.
- Sender identity when signing keys are used and the recipient verifies the signing fingerprint through a trusted channel.
Fold does not protect against
- A compromised device, browser, browser extension, operating system clipboard, password manager, screen recorder, or malware.
- A malicious or substituted public key. Verify key fingerprints through a trusted channel before relying on a key or sender identity.
- A recipient who copies, saves, screenshots, forwards, or publishes plaintext after decrypting it.
- Clipboard managers, cloud clipboard sync, form recovery, crash recovery, browser developer tools, screenshots, or browser extensions that can observe page contents.
- Mistakes such as pasting private keys into chats, URLs, search boxes, logs, issue trackers, or other third-party services. Browser history can preserve anything placed in URLs or search fields outside Fold.
Encrypted packages
- Encrypted output is a self-contained fold:v3 package. It includes the public data needed for decryption, but never includes your private key or plaintext.
- Technically, the package contains an authenticated intent flag, sender ephemeral public key, salt, IV, and ciphertext.
- Signed messages also include a signature that can be checked against the sender's signing public key.
Key handling expectations
- Share public keys freely, but never share private keys.
- Keep encrypted Fold packages separate from private keys.
- Treat signing keys as identity keys. If a signing private key may have been exposed, stop trusting its fingerprint and generate a new signing key.
- Clear sensitive fields when you are done, and clear the system clipboard if your environment keeps clipboard history.