[Cryptography] Proving a Negative (was MAybe he's Adam Back, maybe not)

[Jon Callas]

> On Apr 14, 2026, at 20:57, Peter Gutmann via cryptography <cryptography at metzdowd.com> wrote:
> 
> Nico Williams <nico at cryptonector.com> writes:
> 
>> I also do this, and I'm also not Satoshi.
> 
> Which leads to an interesting side-discussion, how do you prove a negative in
> this case?  Let's say some heavy-set gentlemen turn up at your door because
> someone has decided you're Satoshi, how do you convince them you're not?

I have an anecdote. Maybe you've heard it before, apologies if you have.

A number of years ago (the proper time period will leak), I went on a business trip to New Zealand. I was going through their immigration, and getting the usual set of questions. Why are you here? Who do you work for? What do you do? And so on. I found it interesting because it was more detailed than I usually get. I was entertained, as let's face it, I do boring stuff, really. Not boring to us, but we're people who think boring stuff is interesting, to come right down to it.

Then he asked me about the sorts of things the company did and I replied something like, "Well, ummm, among other things, my company makes the system you're looking me up on." He looks up, gets a big smile and says, "Really?" We start having a great conversation about passport security; how good is contactless, anyway; biometric safety and security; and more.

Somewhere in the back of my mind, Arlo Guthrie is talking about bonding with the guys on the Group W bench. Shut up, Arlo; not now. I mean it, not now. Not. Now. Somewhere out in the arrivals lounge, my co-workers are starting to wonder where the heck I am and deciding they ought to find a seat to sit on.

After a while of grooving with this immigration man about document forgery, MiTM attacks on magnetic coupling, network latency, smuggling, and all sorts of mean nasty stuff, I decide to drop a question on him.

"Have you ever heard of TrueCrypt?" I ask him. See, I told you I was going let you know what time period.

"Oh," he says. "Oh. OH. We know *all* about TrueCrypt."

I asked what he meant. He bristled a bit and said, "You know, we don't search someone's laptop just because they had an apple in their bag. We have to have a real reason to look in a laptop." (To explain the remark about the apple, NZ has strict agricultural controls and minor violations of this, like having an apple in your backpack is an instant NZ$400 fine, on the spot.) He pre-empted my next question by saying, "We know all about the hidden volume. If we see you have TrueCrypt, we just ask you what the password is for the hidden volume."

I asked, "What if they don't have a hidden volume?"

He spluttered, "What kind of idiot uses TrueCrypt and doesn't have a hidden volume?"

"Most people are idiots. What if they don't have one, what do you do?"

He gets thoughtful for a few seconds and then says, "I guess we'd have them sit in one of the holding rooms until they convinced us there was no second volume."

We chatted for a few more minutes, and I went off and met up with my relieved colleagues.

And therefore I ask, what kind of idiot is Satoshi and doesn't have a stash of bitcoins?

	Jon