The solution can be briefly described as an “authenticated power source,” that is, a power source that produces usable power only when activated by the correct key. The solution employs well-known cryptographic building blocks, known for their strength. Moreover, the solution is so simple that it could be implemented, in its simplest embodiment, also at an amatory level (of course, the result would not have the full strength of a professional implementation). The result can be applied as an building block external to the device to be powered or also embedded in the device itself. The former solution is cheaper and applicable to existing devices, the latter is more robust and more difficult to bypass.