> Ultimately, these wireless control devices must simply be built with the assumption that hackers will eventually break in. > In the case of the insulin pump, it should contain hardware-level sanity checking.
However, you can crack any encryption scheme eventually. Encryption doesn't guarantee security—it simply makes the information harder to get at.
By the same token, the lock on your door is security by obscurity. Tell me the type of lock and the position of the 5 pins, and you're in. Take 5 seconds to communicate that over the phone, if you know what you're talking about.
Now, if your security relies upon the attacker not knowing your encryption scheme, then yes. That is security through obscurity.
The term doesn't apply to door locks either, at least not in practice. If I were forever prevented from changing the locks on my house, then yes my security would depend critically on you never knowing about the key. In practice though, I can change the locks at will, and this is an effective remedy against the persistent threat posed by the release of the key.
A good example of security though obsurity is the CSS system used on DVDs, which was designed such that once the key was discovered, the system became forever and irretrievably broken.