Still not the point - they advertise this as a secure device per se. If no-one can reach your 'network' - i.e. your own supposedly isolated bubble of power lines - then you don't need the security; you already have isolation security. If you do need it then a device which has no concept of key privacy is no security at all. Changing keys is not the issue; exchanging keys with any 'suitable' device is the issue.
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@Tony Smith
Still not the point - they advertise this as a secure device per se. If no-one can reach your 'network' - i.e. your own supposedly isolated bubble of power lines - then you don't need the security; you already have isolation security. If you do need it then a device which has no concept of key privacy is no security at all. Changing keys is not the issue; exchanging keys with any 'suitable' device is the issue.