`private-box` implements a lightweight encryption format that lets a sender encrypt a single message for up to seven recipients while hiding both the recipient list and its size. It generates an ephemeral Curve25519 keypair, encrypts a random body key for each recipient, and then uses that body key to secret‑box the plaintext; any recipient can attempt decryption with their private key and will either obtain the plaintext or get `undefined`. The library is aimed at developers building privacy‑focused, public‑read platforms (e.g., Secure‑Scuttlebutt) who need group‑encrypted messages without exposing who the recipients are.