Cardano.KESAgent.KES.Bundle

The Bundle and TaggedBundle types. These represent KES credential "bundles", consisting of the key itself, its current KES period, and an operational certificate ("OpCert"). "Tagged bundles" are tagged with a timestamp indicating their age, and may contain either a Bundle (which indicates a key update), or Nothing (which indicates a key deletion). We need to track key deletions as explicit data points in order to propagate them between KES agents.

Consider a scenario where 3 KES agents are connected as follows:

@@ A == B == C @@

Now the following happens:

1. A key is installed into agent A.

2. The key propagates from agent A to agent B, and from there to agent C.

3. Agent B shuts down.

4. The key in agent A is deleted; agent A no longer holds a key.

5. Agent B restarts.

6. Agent B connects to agent C and receives the key.

7. Agent A receives the key from agent B, thus undoing the delete.

This is undesirable, hence we represent key deletions as TaggedBundles without keys. This way, an agent can hold and propagate a "key deletion" the same way it can propagate actual key bundles. Now the above scenario plays out as follows:

1. A key is installed into agent A.

2. The key propagates from agent A to agent B, and from there to agent C.

3. Agent B shuts down.

4. The key in agent A is deleted; agent A now holds a key deletion.

5. Agent B restarts.

6. Agent B connects to agent C and receives the key.

7. Agent B connects to agent A and receives the deletion. Since the deletion is newer than the key it got from agent C, it deletes the key and stores the deletion.

8. Agent B pushes the deletion to agent C. Since the deletion is newer than the key agent C holds, agent C deletes its key and stores the deletion.