Custom inner payloads
A custom inner payload is designed to work exclusively with the
Herald Envelope payload. If you want a completely
custom payload, see the custom outer payload page.
The inner payload is constructed by a national/state authority and MAY only be
verifiable or readable by that health authority.
There are many reasons individual countries’ inner packets may vary:-
- A different appetite for privacy vs national security, and thus more data needing to be shared
- E.g. one country may be decentralised, another centralised, but using the Herald Envelope payload would allow for international interoperability still
- Requiring the sharing of more epidemiologically useful information (E.g. phones were outside, phone orientation, GPS location)
Note: We recommend the Herald Secured inner payload as this provides full epidemiological information
as well as ensuring national security and individual privacy.
How to implement a custom inner payload
There are only two steps:-
- Implement a Payload provider callback to construct your inner payload on the fly
- Provide size information on the inner payload by either:-
- If using a fixed payload size, tell the Herald protocol what your inner payload size is
- If using a variable payload size, implement a Payload Parser callback
Performing these steps allows your national contact tracing app to continue as-is, but supporting international interoperability by using
the Herald Envelope payload.
Alternatively, implement a custom outer and inner payload.