The video where they
demo this custom PCB also doesn't really prove anything, for what we know it could easily be fake.
Do you think that one company would just make such accusations if they are not true? In addition, Trezor never denied that all the allegations made were completely correct - otherwise, the whole thing would have ended with a lawsuit.
Well, they haven't denied the existence of the vulnerability. I don't know if they got their hands on one of these hacking devices, but again it does not matter, because it's just a technicality. Just a way to make the attack cheaper and faster, which I already said is definitely possible. Just that this one video of a black box and a software with a progress bar doesn't add much value really.
He went a different route and it took him 3 months.
Even for kingpin, the development of the exploit took 3 months, but the execution only a few hours (since he had to wait for the brute-force timing attempt to hit just right).
It's an important distinction to make: time spent researching and time spent executing.
As I said before, I can definitely see how a purpose-made PCB with perfect hard-coded timings and connections can get the job done in 5 minutes and $100 of materials. Just that getting that board will take you months or years of research to find the vulnerability, develop an attack, perfect the attack, and bake it into a PCB.