in this cyber world, nothing is Un-Hackable unless that stays offline, lol
While it is true that keeping electronic devices offline does increase the security a lot, it does not automatically mean that it is unhackable.
Even an offline system does leak information. Whether in form of processing time, electromagnetic fields, etc.. is another question.
But these
side-channel attacks are not pure theory. Successful attacks are definitely a possibility.
AES, for example, can be attacked through cache-timing. The reason for this is that the AES algorithm does use secret data as the index of an array.
Since the access time of an element of an array is dependent on the index, this leads to a possible scenario where an malicious actor could try to decrease the search space a lot.
This attack requires physical access to the machine (or an identical copy of the machine) and access to the same AES implementation.
This shows that even an offline system can be hacked. This depends on a lot of factors.
Such an attack might only happen if someone is targeting you and is ready to spend a lot of resources.
IMO nothing really is unhackable. It all depends on the circumstances.
