
Why Is the TSA Scanning Paper? - pavel_lishin
https://www.schneier.com/blog/archives/2017/05/why_is_the_tsa_.html
======
philipkglass
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 spectroscopy - maybe Raman? Something
like that. It wasn't clear from the article whether the paper products in
their separate bin just went through the same inspection chute as everything
else.

~~~
pfooti
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.

~~~
philipkglass
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.

~~~
kbenson
Or perhaps there was some intel, or some cases where luggage was searched post
scanner that came up with items that should have been caught. That might
trigger a revision in procedures to prevent or reduce future cases, which is
how I would expect and want a program that was actually meant to reduce danger
to operate.

------
exabrial
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.

~~~
sandworm101
Agreed. "Scanning paper" has spying implications. They are just xraying it in
its own bin.

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

~~~
dunham
I always presumed that they wanted the laptops in a separate bin because they
were comparing them to a set of known images (of commercially sold laptops),
but perhaps I'm giving them too much credit.

~~~
goodcanadian
I doubt it. There are too many makes and models out there to make this a
reasonable thing to do. I imagine that it is just to see things more clearly.
A laptop is many layers of densely packed electronics. It would be very easy
to hide explosives (in place of the battery, for example) and triggering
mechanism in there.

~~~
fvold
"In place of"? It's trivial to cause a lithium-ion battery battery to explode
if you know how. Don't tell TSA, though, or you're going to have a very boring
flight.

~~~
sandworm101
Burn yes. Pop yes, but not the sort of explosion necessary to damage an
aircraft. That guy on youtube making "grenades" from batteries ... they are
more firecracker than weapon. You could do more damage with a bottle of vodka
and a match.

~~~
jmcdiesel
Anyone who's flown RC aircraft in the past decade knows all too well about
this..

Spectacular light show, a good burn... yeah. Thats about it though... It
wouldn't be worth a terrorists time... it would just be a light show and a
smoke show, could start a fire, which would be bad, but honestly fires get
suppressed pretty quick on modern airliners as long as they aren't started in
the cargo area and ember for a while... in the end, any attack carried out
with a LiPo/LiIon would just be an inconvenience...

~~~
sandworm101
The scenario that keeps some pilots up at night is unsecured human cargo in a
panic. A medium fire won't ignite the plane but it will fill the cabin with
fumes. Those drop-down oxygen masks are useless in such scenarios. Get enough
people to panic, to run fore or aft, and one could create a crush event or
even destabilize the aircraft.

~~~
jmcdiesel
From storeis though, panicked passengers in flight tend to stay calm... there
is a sense of helplessness and acceptance that takes over pretty quick when
you realize there isnt anything you can do

------
rosalinekarr
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 that data can be more easily copied and
analyzed?

~~~
djsumdog
Or it's simpler than that: security theatre. We're adding a new level of
annoyance so people have this false impression their jobs aren't totally
beyond worthless.

Fuck the TSA and the airlines. These days I'll pay more to take am AmTrak or
just drive. Next time I fly, it will be after taking a train to Canada first.
If I have to fly internationally, I'd rather not fly out of a US airport. I've
flown through over a dozen countries, and yes, it is getting ridiculous
everywhere, but America is still the worst. Especially when it comes to pat
downs. No other country I've been through did pat downs except Moldova; and
even theirs weren't anywhere near as bad (typically police arms/leg pat downs.
No reaching under your belt or any other TSA bullshit for the false-
positive/random-number-generator they try to tell you are body scanners).

~~~
oasisbob
> These days I'll pay more to take am AmTrak or just drive.

I take it you've never been searched by Amtrak police. Once on a cross-country
trip all my belongings were searched twice - in Chicago where I departed, and
again mid-trip.

It's not a great time.

------
tuna-piano
Kansas City Airport doesn't use TSA screeners, they have a private contractor
doing the screening:

[https://www.tsa.gov/for-industry/screening-
partnerships](https://www.tsa.gov/for-industry/screening-partnerships)

That said, it seems like this policy is likely a TSA imposed pilot program:

[https://thepointsguy.com/2017/05/paper-products-new-tsa-
secu...](https://thepointsguy.com/2017/05/paper-products-new-tsa-security/)

~~~
exabrial
I don't believe this is true, how does one tell? They appear to be TSA agents,
in the blue uniforms with the TSA badges

~~~
tuna-piano
It's true. Turns out blue shirts can be worn by just about anybody.

Here's a story from last summer about the private security at Kansas City
Airport:
[http://www.kansascity.com/news/local/article79795177.html](http://www.kansascity.com/news/local/article79795177.html)

~~~
bogomipz
Oh interesting. I am curious is the experience of the privatized screening any
better?

Or is the amount of humiliation, infantilizing and browbeating of regular
honest people about the same as the non-privatized TSA?

There was big uproar about privatizing the TSA about a year ago when the time
spent in lines was growing even more excessive. That narrative about
privatizing seemed to go dark. Is the Kansas City Airport itself a pilot
program for privatization of the TSA?

~~~
madengr
Yes; I live in KC. The ones in MCI are polite, as opposed to Baltimore where
they strut around barking orders.

Of course MCI had a distributed security and gates, so they are smaller and
thus quieter.

~~~
exabrial
Yeah I think the distributed security has a lot to do with customer
satisfaction. The horseshoe design is really efficient for plane parking and
the drop/pickup. Unfortunately, it's terrible for logistics like transfers :/

~~~
madengr
I think it's the best airport in the country. I can get from plane to car in 3
minutes. But yes, transferring airlines would be a pain, though flights on the
same airline are usually within the same security zone.

Unfortunately the KC politicians keep scheming to build a new one. Fortunately
the population wants to keep it.

------
wwwigham
Given that I've had this happen to me at a checkpoint (in Seattle) and had it
explained to me, I think I have a reasonable potential answer: Stacked paper
produces false positives in the scanning machines which can be flagged as
suspicious substances. By separating the paper into a separate bin, it can be
more quickly inspected by human eyes and the flag cleared, allowing the
security line to be cleared more quickly.

~~~
chrismeller
Perhaps a bit cynical, but that is exactly the reason I would expect from the
TSA.

It's not that they're enhancing their screening of anything in particular,
they're just helping you get through more quickly... sureeeee.

------
Havoc
I'm gonna go with TSA is looking for innovative new ways to inconvenience
travellers.

~~~
r00fus
Any organizations' first imperative is to sustain itself. If security theatre
is all they have, that's what we'll get and more of it.

------
valuearb
If the TSA was shutdown entirely leading to terrorists blew up 10 planes a
year in the US, flying would still be as safe as it was in the 1960s.

[http://www.sfgate.com/nation/article/U-S-commercial-
airlines...](http://www.sfgate.com/nation/article/U-S-commercial-airlines-
have-safest-decade-ever-2435203.php)

~~~
wand3r
For those w/o a working knowledge of 1960s air safety; are you saying removing
the TSA would make us safer, less safe or simply that we tolerated the same
level of safety w/o TSA 50ish years ago?

~~~
valuearb
I'm not advocating removing the TSA entirely, just pointing out that we are
paying a heavy price for a likely small benefit.

Locking the cabin door virtually eliminated the threat of turning jetliners
into terrorist weapons at a tiny cost. But on top of that we've cost the
country maybe a trillion dollars in excessive and invasive security procedures
to prevent planes from being blown up. The TSA is only one part of those
costs, longer travel times, reduced travel and lost liberties are a big part
of it.

The value to terrorists blowing up an airliner is relatively small, there are
far easier and cheaper ways to kill a few hundred people to make a political
statement.

So my real question is, if we reduced spending on airport security, and
reduced the level of security significantly so that we shaved 15 mins on
average off every trip, would it be worth accepting a plane being blown up
every few years?

Every year the US has nearly 1 billion trips by air. If you value travelers
time at $20/hour, saving 15 minutes per trip directly saves nearly $5B a year.
If the cost of saving those 15 minutes per trip is 50 lives per year, we are
valuing each of those lives at $100m each. That seems incrediably excessive to
me. Of course this is just a rough estimate, run your own numbers but it's
hard to imagine the costs get down to a barely reasonable $10M per life level.

and remember that doesn't include the cost of the TSA or the cost of flights
not taken.

~~~
DKnoll
The TSA doesn't just exist to stop terrorism. Also if the US didn't screen
passengers, many other nations likely wouldn't accept flights originating from
it.

How are you assessing the value of a human life?

~~~
valuearb
I never advocated not screening passengers, just doing it more efficiently
even if slightly less effective.

How are you assessing the value of a human life? I don't know of any study has
ever gone above $10M.

------
robert_tweed
My theory: they aren't looking for paper, they are trying to rule it out as
something else.

My understanding of these scanners is that they colour-code "organic" and
"inorganic" material differently. Explosives generally show up as organic.

Now, if you have a block of such organic material in just the right position
next to some electronics, the conveyor gets stopped and you will be taken to
one side and asked some very direct questions about the contents of your bag.

I know this because I once had a protein bar in the same bag as a portable DVD
player and that aisle went into lockdown for about 30 minutes because it
looked exactly like a bomb, from all angles, in 3D. Expert called over, agreed
they couldn't start the conveyor until they knew it was safe.

My guess is that paper (in the form of small pads) is the commonest cause of
this type of false positive.

------
madamelic
I can't wait till we have to travel in paper smocks, chained to our seats like
the criminals we truly are.

~~~
camiller
What about those of us that can't afford first class!

~~~
ebcode
No smock for you!

------
emiliobumachar
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?

~~~
swiley
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.

~~~
wyldfire
I kinda doubt those body scanners have anything remotely close to the spatial
resolution required to find text written on a sheet of paper.

~~~
CyberDildonics
He said the same band. That wouldn't have anything to do with spatial
resolution.

~~~
wyldfire
Sorry. I inferred that suggesting this meant (in the vein of this "tinfoil hat
time" thread) that the body scanners might have the capability to read text
from paper.

------
CaliforniaKarl
Summary: Bruce doesn't know, and so he is asking his readers.

~~~
YCode
Yes, it would have been nice if the title explicitly stated that... i.e.,
"Does anyone know why the TSA is now scanning paper?"

~~~
jeron
That's Bruce's fault, OP just copy-pasted the title

------
r00fus
I had my bag pulled out of the scanner while at SAN - was very frustrating as
I was going between the 3-9 gates and the 1/2/2A gates on a connection -
amazingly had to go back through security - and had only a few minutes before
my connection left.

In an exasperated voice I asked the security person why she had to dig through
my bag and she indicated that the paperback novel that I had in there was the
trigger.

So I replied - guess I'm not going to take a paperback next time. Another
freedom impinged.

------
sandworm101
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.

~~~
marcosdumay
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.

~~~
djrogers
X-ray machines don't look at chemical composition, they care about density.
Paper is quite dense, and a thick enough pile of it will show up as a solid
block of 'something'.

~~~
marcosdumay
They differ elements by row of the periodic table, and modern ones have
special filters for separating a single interesting element from the rest of
its row.

------
ckrailo
I found this story by checking Google for updates in the news... sounds like
the TSA has reversed course:

[http://www.bizjournals.com/kansascity/news/2017/05/05/tsa-
fo...](http://www.bizjournals.com/kansascity/news/2017/05/05/tsa-folds-new-
checks-on-passengers-paper-goods.html)

------
alimoeeny
I think the point many people are missing is that this is a "new" development.
All the talk about paper composition / features could overlap with other
banned material cannot be new.

------
cmurf
I found this, it may or may not be related. The gist is relatively recent
research (2011) discussing using x-ray refraction rather than just attenuation
and is capable of "creating precise images of the contours of all objects".

A New Generation of X-ray Baggage Scanners Based on a Different Physical
Principle www.mdpi.com/1996-1944/4/10/1846/pdf

------
nealabq
Maybe they're looking for flash paper.

[https://en.wikipedia.org/wiki/Nitrocellulose](https://en.wikipedia.org/wiki/Nitrocellulose)

~~~
evan_
seems like regular nitrate sniffers would catch that, and x-rays would not

------
eli
Seems like TSA does a lot of pilot programs that (luckily, imho) don't end up
going anywhere. They once set up a folding table and searched everyone
boarding my Greyhound bus.

~~~
Arizhel
They tried doing that at an Amtrak station a while ago and were forcibly
removed from the premises by Amtrak police.

~~~
djsumdog
That's awesome. I remember hearing about their VIPR squads harassing people
after they had disembarked a train at their destination. I'm glad Amtrak
fought their bullshit.

------
badloginagain
Does cash have a unique identifier that can be scanned for? If someone was
trying to bring a wad of hundreds in a hole cut out in a book, maybe they'd be
looking for that?

~~~
DoubleCribble
Yep. Metallic ink is used in your green(/blue/red)backs.
[http://www.dailymail.co.uk/news/article-2120883/A-step-
spywa...](http://www.dailymail.co.uk/news/article-2120883/A-step-spyware-
Metal-detectors-tell-cash-pocket.html)

------
glup
I thought this might have something to do with printer steganography [1] but
not if they are just X-raying the paper. Also I'm not sure whether that
practice is ongoing--I haven't heard anything about it for years.

[1]
[https://en.wikipedia.org/wiki/Printer_steganography](https://en.wikipedia.org/wiki/Printer_steganography)

------
makecheck
This sounds more like the "department of imagined threats" justifying its
existence, not actual security.

Even if there is ANY possible risk, what was their analysis? The odds of this
are probably lower than being struck by lightning.

The only new things I want to hear out of the TSA each week are: which rules
have now been REMOVED, and how many fewer minutes security lines are taking on
average.

------
pavel_lishin
I've had agents ask me to take out a card game from my bag - apparently the
thick stack of cards can look like C4 on the scanner.

------
tyingq
Maybe some intelligence that people are inserting sheets of metal foil into
stacks of paper to attenuate the x-rays and hide something underneath?

Assuming the airport X-ray machines aren't that powerful, I would guess that
15+ sheets of foil inserted into a book or similar might mask something
underneath it fairly well?

~~~
alimoeeny
but it would show up as masked or dark or low energy, then they can mark as
"needs manual search". That does not require forcing "all" papers out of all
bags.

~~~
tyingq
I was assuming many thin sheets of foil, each separated by several pieces of
paper might be more subtle, than say a slab of lead. Subtle masking vs
completely hiding something else under it.

------
Trung0246
Maybe this?

[https://en.m.wikipedia.org/wiki/Printer_steganography](https://en.m.wikipedia.org/wiki/Printer_steganography)

------
falcolas
A friend of mine was also queried about books in his bags _before_ going
through security. I was two steps ahead of him and was not.

This was in a comparatively small airport in Montana, so it's not an isolated
trial, if it is a trial.

------
evan_
Wasn't there a scene in one of the recent Bond movies where a huge pile of
cash had been treated in some kind of chemical that turned it into a bomb?

~~~
alan
The World is Not Enough is the movie you're thinking of. From 1999, if you
want to call that recent; going back 18 of the 55 years of Bond movies.

~~~
evan_
that's right. I was thinking it was one of the Daniel Craig films. In my
defense I remembered the explosion was at MI6 and MI6 blows up twice under
Daniel Craig's watch...

------
madengr
I was at MCI on Sunday and can verify this. Even with pre-check, I had to
remove my engineering pad from my carry on pelican case.

~~~
jedberg
Oh man, even with pre-check? So it completely defeats the point of pre-check
then by making everyone take something out of their bag. Ugh.

------
brianwawok
I got a paper game (star realms) pulled out of my bag last Sunday.
Interesting. Was about 120 playing card size pieced of paper.

------
clebio
Is there an opt-out for this? What if you just refuse -- can they deny you
boarding, and is that legal?

