hi Stan! hope all good on your side.

You understood the EphID check correctly and yes their creation is fully deterministic and reproducible given the same SK and the same “broadcast key” which in Zenroom is `Decentralized Privacy-Preserving Proximity Tracing` aka `446563656e7472616c697a656420507269766163792d50726573657276696e672050726f78696d6974792054726163696e67`

Infected subjects will give their SK to the server to be voluntarily traced, because that’s the whole point. The system is made so that after the emergency there is no trace linking the identity of the person to the SK.

All this is better described in the DP-3T whitepaper, but I think you went pretty far just reading code :^)