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Why Is the TSA Scanning Paper?

schneier.com

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Re: Why Is the TSA Scanning Paper?

#41

Post by learc83 »

marcosdumay wrote: post #17
sandworm101 wrote: post #5

Because blobs of paper look to similar to blobs of potential explosives when xrayed. They arent scanning it so much as removing it from the scan of everything else.

Blobs of explosive normally have a chemical composition that is different from blobs of paper in a way that a X-ray scanner would detect. If somebody created an explosive that could pose as paper for X-ray, that would be noteworthy.

>Blobs of explosive normally have a chemical composition that is different from blobs of paper in a way that a X-ray scanner would detect.

How is that? If a block of explosives is close to the same density as a stack of paper, they're both going to show up as similar colored blocks on the X-ray.

Re: Why Is the TSA Scanning Paper?

#42

Post by learc83 »

csydas wrote: post #37
sandworm101 wrote: post #16

Earlier quoted context omitted.

It is the cellulose in the paper. Blocks of it are homogenous enough that they look similar in density to something dangerous. Add in ink, glue and other materials commonly soaked into paper and the situation is not totally unreasonable. https://en.m.wikipedia.org/wiki/Nitrocellulose

I lack the expertise to comment on the sensitivity of the cellulose specifically, but the metro stations where I live will perform random stops as you enter, and the monitors are in plain sight. Notebooks, stacks of paper, and note cards are usually pretty clearly detected by whatever software they're using to help highlight items. It seems weird to me that there could be such difficulty with TSA scanners versus the…

>Notebooks, stacks of paper, and note cards are usually pretty clearly detected by whatever software they're using to help highlight items

How do you know the problem isn't that the software flags dangerous items as paper incorrectly (which I think is the mostly likely problem here)? I doubt you've seen the X-ray image of someone smuggling nitrocellulose.

The software is just using density--if you have an explosive of similar density to paper, it's probably not going to flag it.

Re: Why Is the TSA Scanning Paper?

#43

Post by nathancahill »

ferentchak wrote: post #13
sandworm101 wrote: post #10

Earlier quoted context omitted.

Agreed. "Scanning paper" has spying implications. They are just xraying it in its own bin.

They seem to like dense things to be in their own bin. Books are pretty dense.

I recently flew with 20 lb of cheese. Definitely got re-scanned. Cheese is dense.

Re: Why Is the TSA Scanning Paper?

#44

Post by pfooti »

philipkglass wrote: post #21

My guess, already voiced by "Ron" on Schneier's blog: they're looking for nitrocellulose. Nitrated paper is not obviously different in appearance from ordinary paper. Sheets of nitrocellulose have negligible vapor pressure and little dust so they could be missed by other means like the "puffer" detectors. If they're putting these materials through a separate machine my guess would be another detector based on optical…

They're not putting them through a different detector, though. They take out the books and all papers the passenger has, put them in one of the normal trays, and run the trays through the xray.

My wife traveled out of Kansas City last weekend and was subject to this. She's a teacher, and traveled with grading, so they took out tests, her books, everything that was paper. The line agent said they were worried about papers being used to obfuscate other things in the xray machine. But that was the line agent, so he could have been (a) uninformed or (b) lying.

Re: Why Is the TSA Scanning Paper?

#45

Post by philipkglass »

pfooti wrote: post #44
philipkglass wrote: post #21

My guess, already voiced by "Ron" on Schneier's blog: they're looking for nitrocellulose. Nitrated paper is not obviously different in appearance from ordinary paper. Sheets of nitrocellulose have negligible vapor pressure and little dust so they could be missed by other means like the "puffer" detectors. If they're putting these materials through a separate machine my guess would be another detector based on optical…

They're not putting them through a different detector, though. They take out the books and all papers the passenger has, put them in one of the normal trays, and run the trays through the xray. My wife traveled out of Kansas City last weekend and was subject to this. She's a teacher, and traveled with grading, so they took out tests, her books, everything that was paper. The line agent said they were worried about pa…

Trying to de-clutter the images by separating paper would fit the observed procedure too. It seems a little odd that it would start only now. Maybe screener testing recently showed better performance when paper is separated out.

Re: Why Is the TSA Scanning Paper?

#46

Post by [deleted] »

rosalinekarr wrote: post #23

There seem to be a lot of people theorizing that it could be something about the paper itself that they're looking for, i.e. flash paper, paper circuits or physical one-time encryption pads, but what if it's not about the paper at all? Maybe, the TSA is simply trying to discourage passengers from traveling with or using paper, thereby encouraging people to store their information digitally on phones and laptops where…

[deleted]

Re: Why Is the TSA Scanning Paper?

#47

Post by [deleted] »

exabrial wrote: post #29
UnoriginalGuy wrote: post #25

Earlier quoted context omitted.

Going a little off topic now... I'm surprised nobody has combined 3D X-Ray Scanning with computer vision technology. At the moment we're depending on the human eye flicking between three dimensions and spotting bad things, with very basic shape detection to "hint" at objects of interest. This system kind of works, but has human error weaknesses. If you fed 3D X-Rayed objects into a computer vision engine, eventually…

That already exists, but are commonly used on baggage, not at checkpoints. I can't remember what airport I was at, but they were scanning bags in the terminal area before loading them on a belt.I saw a TSA employee stick a bag through the machine, and the machine found a bottle of wine wrapped and taped in bubblewrap and outlined the wine bottle with a red outline. The guy they set the bag off to the side (presumably…

[deleted]

Re: Why Is the TSA Scanning Paper?

#48

Post by Rebelgecko »

exabrial wrote: post #6

I flew out of MCI (American Airlines) on Sunday evening, confirmed this definitely happened. They asked for books, papers, notebooks, etc. However, I disagree with one point in the article: I didn't witness them "scanning" the documents with a scanner. They went through the Xray machine in a separate bin, much like your laptop does. Perhaps I missed something.

On a flight a year or so ago, I had a TSA agent open up a book I had in my carryon to half a dozen different places to swab for explosives. Not sure if that's standard procedure though, I think I had annoyed him earlier.

Re: Why Is the TSA Scanning Paper?

#49

Post by coldpie »

swiley wrote: post #8
emiliobumachar wrote: post #3

Okay, tin foil hat time. Maybe they have new machines that can see the print through the paper, and actually scan and store the contents of all these papers in a timely fashion?

There was an MIT reasearcher a while ago (it may have been posted here) using THz wave radar to do this. I think it's the same band (ish) the body scanners use.

This is only tangential (I don't think the TSA is doing this), but this is similar to a fascinating technique for finding writing on discarded paper used as filler in bindings and such in old books.

https://medievalbooks.nl/2015/12/18/x-rays-expose-a-hidden-m...

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