introduction-protocol.md

+```mermaid
+sequenceDiagram
+Alice-X+Repeater: Add contact
+Repeater--X-Alice: repeater's public key, timestamp
+Alice-X+Bob: repeater's public key, timestamp
+Bob--X-Alice: Bob's public key, timestamp, mac
+Alice-X+Repeater: Bob's public key, timestamp, mac
+Repeater->>Repeater: shared secret (ECDHE)
+Repeater->>Repeater: create sym. key from shared secret
+Repeater->>Repeater: derive transport keys
+Repeater--X-Alice: repeater's mac, contact id, transport properties
+Alice-XBob: repeater's mac, transport properties
+activate Bob
+Bob->>Bob: shared secret (ECDHE)
+Bob->>Bob: create sym. key from shared secret
+Bob->>-Bob: derive transport keys
+Bob-->Repeater: Secure communication
+```
+The asymmetric keys are newly created ephemeral keys.  
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