((("Lightning encrypted transport protocol","high-level overview")))((("Noise_XK","high-level overview")))Using the notation laid out earlier, we can succinctly describe the `Noise_XK`
as follows:
as pass:[<span class="keep-together">follows</span>]:
```
Noise_XK(s, rs):
<- rs
@ -599,7 +599,7 @@ Where `len` obtains the length in bytes of the Lightning message.
* The nonce `sn` must be incremented after this step.
* A zero-length byte slice is to be passed as the AD (associated data).
4. Finally, encrypt the message itself (`m`) using the same procedure used to
encrypt the length prefix. Let this encrypted ciphertext be known as `c`.
encrypt the length prefix. Let this encrypted ciphertext be known pass:[<span class="keep-together">as <code>c</code></span>].
+
The nonce `sn` must be incremented after this step.