Update X-Protocol Interworking Use Case with Security and Privacy Considerations about wot-usecases HOT 2 OPEN

Here I am

from wot-usecases.

Link correction: https://github.com/w3c/wot-architecture/blob/master/USE-CASES/X-Protocol-Interworking.md

Comments (independent from security&privacy):

• The notion "device" is not welcome by all with stakes in the considered scenario => consider to make namespaces more explicit (OT also has non-devices "devices" that are important) or consider a more generic term that does not clash
• The notion "interoperability" is difficult as well (valid on macro-level where one "device" implements components in multiple stacks e.g. OPC-UA and PROFINET, potentially misleading on micro-level which considers components belonging to one stack e.g. OPC-UA and PROFINET are non-interoperable like HTTP and SMTP are [but computers implementing HTTP and SMTP components may interact])

Comments (re security&privacy):
I think the use case needs some more clarification/refinement in order to suggest a (meaningful) proposal for a security&privacy section. For that reason I leave it for the moment with some early input:

• If two (or more) non-interoperable protocols are used in an information exchange between two (or more) endpoints (think of HTTP for the first mile and SMTP behind that) then:
  -- There is no E2E security/privacy between these endpoints - on protocol level i.e. layers 2..7a
  -- If there is E2E security/privacy on the level of application data objects depends - on many things such as info representation, encapsulation strategy, key management...
• Intermediaries are an obstacle to security&privacy that can be achieved. Whether and to which extend depends on their nature (protocol gateway, proxy, router, switch...) as well as security mechanisms, for instance:
  -- S/MIME can traverse protocol gateways, proxies, routers, switches (but not/hardly language boundaries)
  -- HTTP-over-TLS can traverse switches, routers, proxies but not protocol gateways
  -- IPsec can traverse routers and switches but not proxies and protocol gateways
  -- MACsec can not traverse anything (including switches)

from wot-usecases.