&gt; Come to think of it, backdoors are fundamentally &quot;security by obscurity&quot;. Or insecurity through obscurity, depending on your POV.<p>This one is. But they aren&#x27;t always.<p>For example, if a manufacturer put in a support&#x2F;recovery backdoor, documented it, and utilised a secret that only the end user and manufacturer should know (e.g. something on the physical label), then that would be a backdoor while not relying on any obscurity for its security (or no more than a password does).<p>The biggest difference between a &quot;good&quot; backdoor and a &quot;bad&quot; one is if it is documented. If the manufacturer is too scared to document it then it likely sucks and they know it.