[Cryptography] Article on Encryption

Jon Callas jon at callas.org
Sat Apr 10 17:46:29 EDT 2021



> On Apr 9, 2021, at 18:38, Whitfield Diffie <whitfield.diffie at gmail.com> wrote:
> 
>     Anyone have any idea what this
> 
> https://interestingengineering.com/infrared-radiation-from-our-hands-could-be-the-future-of-encryption

Grouchily, it's a combination of BS with some possibly interesting things in it.

Sorting through the BS would take a long time and as fun as that would be, I'm not in the mood, so let's skip to what's really there.

They write a message onto an aluminum panel and then spray polydimethylsiloxane on top of it which apparently scatters (I might be using the wrong word -- "hide" might be better) the image among ambient IR thus making it invisible, and then using another IR source (a hand) whatever the spray is doing is overcome and the message is visible.

Then it veers back into BS. Part of this is that this is quite likely a really cool and innovative hidden ink system, where the message is hidden by a coating and then the optical properties of the coating are overcome by those in the know. This is, of course, not encryption.

Part of the BS is musing about how since all our bodies are different, then somehow our body could become a "key" so messages could be tailored to a person. The BS is hidden in the world "could" as often is the case. Yeah, sure, could. To disprove a "could" I have to prove "couldn't." However, let us note that there's nothing in here about how a give person's IR qualities change over time (ever have cold hands?) and of course would be affected by weight changes and even hydration. 

Another part of the BS is that to use this as a tailored messaging system, we'd have to somehow encode Alice's uniqueness and send it to Bob. (And yes, now we're getting close to a thing that is kinda like encryption.) And then Bob has to tailor the coating in such a way that it can be revealed by Alice. One presumes that we also want the message not revealed by Eve, nor even The Post Carrier or the post office sorting machine. One presumes we also want the coating to be indistinguishable from lots of things, but there's a huge debate we can have, since back into real cryptography realms, pseudorandom things stick out like sore thumbs. There is much to discus, so let me just say there are a lot of practicalities that were lossily compressed into the word "could."

Popping back, this looks like a potentially interesting way to do some fun things. I mean, I'd look at this for how you could put an authenticity mark on a package, perhaps. (Note that I'm eliding away a use case for an authenticity mark that's invisible except under the right conditions.)

It reminds me, perhaps of the sort of moon runes that were on Thorin Oakenshield's map to Smaug's treasure, or in other places in Tolkien. Secret writing is cool, after all. It might even be useful. It might even be the too-clever-by-half stuff that makes for a good plot point, but doesn't survive a security analysis that the Noldorin were somewhat notorious for.

	Jon





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