This is why the private signing sessions were completely worthless as evidence. To do this requires adding 3 lines of code. I did this with ElectrumSV because I had it handy, but the relevant code in Electrum is almost identical. Start to finish it took about 30 mins including finding where to change the code. AFAIK I know all of the signing sessions except Gavin's were done on Craig's laptop, with no checks to ensure it wasn't a modified version. Gavin at least recognized this and insisted it be done on a new laptop. What I didn't know until I read Gavin's deposition in the Kleiman case a while back (all 440 pages of it), was that according to Gavin, Craig had unobserved control of the laptop for long periods while it was being setup prior to the signing. In which case it would be trivial to install a modified version from anywhere on the internet. Gavin didn't verify the software himself so this would have gone undetected. The easiest way to solve this problem was to give people a copy of the signature to verify for themselves, but that's the one thing that Craig would never allow. Why? Well if he knew the signatures wouldn't verify the answer is obvious. If he knew they would not so much. If he really was planning to do a public signing or move a coin (which amounts to the same thing) then it couldn't do much harm. If he was worried that proof of signing would bring the wrath of the US govt down on his head, then how was he ever planning to do the public signing? If he never had any intention of doing it, then I still think if they really wanted to extradite Satoshi Nakamoto, then him going on TV and telling the world he was Satoshi would have been sufficient evidence for them to do it.