feat: add diagram

book/src/intro.md

@@ -36,3 +36,16 @@ can then be verified by anyone / any chain (assuming PKI).
 - Linear communication complexity: $n \times (m + r)$ ($m$ = message size, $r$ = response size)
 - Minimal, constant latency
 - Maximal throughput
+
+Here is a high-level diagram of the happy-case flow:
+
+![DATO simple flow](./assets/dato_simple_diagram.png)
+
+1. A client sends a message $M$ to all $N$ validators
+2. Each validator signs the message and their local timestamp, and sends it back to the client
+3. The client waits until a quorum of $2/3$ signatures is reached, and then calculates the median timestamp
+4. The client aggregates the signatures into a quorum certificate that can be used to prove the timestamp
+
+On top of this functionality, DATO also provides a way to obtain _unavailability_ certificates
+for individual messages, to prove that a message was not seen by a quorum of validators at a
+given time. This is useful for attribution in the case of censorship.