code: func Open(out, box []byte, nonce nacl.Nonce, peersPublicKey, privateKey nacl.Key) ([]byte, bool) {
  	sharedKey := Precompute(peersPublicKey, privateKey)
  	return secretbox.Open(out, box, nonce, sharedKey)
  }
docs: // Open authenticates and decrypts a box produced by Seal and appends the
  // message to out, which must not overlap box. The output will be Overhead
  // bytes smaller than box.