This is the second post in my ongoing series on the troubles posed by high-speed signals in the hardware security lab.

What is a High-speed Signal?

Let’s start by defining “high-speed” a bit more formally:

A signal traveling through a conductor is high-speed if transmission line effects are non-negligible.

That’s nice, but what is a transmission line? In simple terms:

A transmission line is a wire of sufficient length that there is nontrivial delay between signal changes from one end of the cable to the other.

You may also see this referred to as the wire being “electrically long.”