hi i'm giggs welcome to when electronics
and deception collide a short talk about
historical and modern uses of technology
to mislead and deceive
i'm the
founder of compound electronics on
freenode may she rest in peace we've
moved over to libera chat if you haven't
moved with us yet
i've been a volunteer at the hhv for
about eight years
ish
now
regarding this talk keep in mind that
this is all hobby stuff for me i might
be wrong about something
so what can be seen cannot be unseen
we'll obviously get a lot more into this
later but there are elements to
polygraph testing that don't really work
right if a person being examined knows
how they work
if you need to do this for your job
consider whether you should continue
watching this or not
that said everything in this
presentation is public information there
shouldn't be anything secret
you have been warned
related to the idea that knowing how a
test works can ruin the test back in
2009 i used to edit wikipedia i noticed
the debate raging on the back and
discussion pages about the rorschach
inkblot test
regarding whether the images for the
test which had fallen into the public
domain should be published
you may think that a test where you look
at random images of inkblots wouldn't
have the correct answers or incorrect
answers but that's not the case the test
actually has a set of same answers and a
set of insane answers and
those are the incorrect and incorrect
answers
i wrote up a small blurb about the
debate for slashdot which got posted on
the front page in 2009
i expected that would be the end of it
a geeky story about slashdot or four
slashdot about an argument within
wikipedia and that's it
turns out
that gnome cohen a reporter for the new
york times also apparently read slashdot
he picked up the story it caused the big
media flurry there were morning news
shows where they were broadcasting the
actual rorschach images where they were
giving each other the test playing games
seeing if they would get the right
answers or not
despite this leak in the strong evidence
that the test is suited scientific it's
still sometimes used in court cases
so on to the actual topic of the talk
electronic deception
one of the earliest writings that
documents electricity other than
lightning
is already ascribing powers to it that
it doesn't have
plenty of the elder wrote extensively on
natural remedies around 77 a.d including
the electric torpedo fish which he said
could
numb the most vigorous arm and rivet the
feet of the best runner
he then goes on to list nine very
questionable medical treatments based on
the mysterious powers of this fish
including one for precedence of the
rectum
which apparently either means prolapse
or hemorrhoids it wasn't entirely clear
and it's treated by applying the
electric fish topically i don't know if
they mean alive or ground up but either
way
sounds pretty gross
skipping forward eighteen hundred years
or so not very long after the early work
in harnessing electricity and magnetism
had just been done
one of the first non-scientific uses of
electricity was in the stage show of
robert hooden
his trick with the light and heavy chest
was to invite a boy and a strong man
from the audience a small boy could lift
the chest while the strong man could not
it relied on a strong electromagnet
under the stage and a metal steel plate
in the bottom of the box and he would
turn the electromagnet on and off to
control whether the box was light or
heavy
most of the audiences at the time had no
idea what electromagnetism was it had
only really been discovered and
documented 30 years before this
moving on to a slightly more
controversial topic nikola tesla tesla
invented and proved numerous things we
still use today but he was also intense
especially toward the end of selling
this idea of long-range wireless
electricity
he gave shows where he he would hold
lamps and strong electric fields and
they would light despite not being
connected to anything
most of us have seen similar
demonstrations of fluorescent tubes
under power lines and things like that
and they light up
the problem is the electric fields drop
off with the inverse square of the
distance despite tesla's claims
otherwise
so was tesla being deceptive it's hard
to say he probably believed what he was
saying that's the problem that runs deep
when you look at these issues
separating the charlatan from the true
believer
is not always easy
what we're about to look at are a few
technologies that certainly have their
share of true believers
if you yourself haven't if you yourself
happen to be a true believer don't take
this as a personal attack but maybe take
a step back and evaluate whether your
belief is misplaced or not
so first a personal anecdote my uncle
recently
called the carpet cleaning service and
they brought in these high-powered uv
lights to detect cat urine
they proceeded to say his entire house
was covered in cat urine that they'd
need to tear out all the carpets and
replace at least the pads
my mom showed me these pictures the
thing is uv light causes many things to
fluoresce not just urine spilled food
liquid detergents club soda lemon juice
toothpaste it's a pretty big list
i mean yeah that carpet's pretty dirty
but maybe give the cat a break
so what makes a good modern deception
prop we can look at the field of ghost
hunting for some easy examples
it should be something that produces
noisy fuzzy output with lots of
artifacts preferably not totally random
but with some kind of opaque internal
functioning
the vague property of being sciency
helps link credibility as well
people want to see patterns they want to
confirm what they already believe
these sorts of devices are tools of
confirmation bias that let people find
the patterns that they're looking for
so we got a list here
you can read it
they all have the same sort of thing
night vision video artifacts audio
recorders
let's move on to the fmri the functional
f the functional mri it's a tool that
was developed in the 1990s and measures
blood oxygenation in the brain that's
all it does
blood oxygen oxygenation is somewhat
decent proxy for telling us what areas
of the brain are being more active but
that's about where the good parts end
it collects an image of between 130 and
160 000 voxels
with noise inherent in the capture it
has time-based blurring which means that
when a part of the brain demands more
oxygen it takes several seconds to ramp
up the detection on the mri when the
demand of blood goes down it keeps
showing up for a while as well
head movements can throw it off in
spatial resolution but the main problem
is that it's generating a large and
noisy data set with over a hundred
thousand potential correlations
p hacking is the term given to the idea
that if you try enough independent tests
you'll eventually find a positive answer
if your p-value threshold is five
percent and you try something 20 times
you'd be expected to find one false
positive
so
this is a fish in an fmri notably it's a
dead fish a salmon
craig bennett of uc santa barbara was
frustrated with the situation of fmri
studies being released that were not
doing multiple comparison corrections
which are mathematical techniques to
help negate the inherent p hacking that
fmri
correlations give
so i went to the store bought a dead
salmon put in the fmri and then asked
the dead salmon to explain what emotions
were being depicted in the pictures that
he showed to the dead salmon
the fmri did not fail to show the
response of the dead fish you can see
the voxels lighting up there
so the study making fun of the lack of
use fixed fmri right well
fast forward to 2016 anders eklund ran
some tests on large sets of control data
but the p-value of o5 5 false positives
were expected instead he found false
positive rates as high as 70 percent
it turns out the normal the noisy data
with opaque software still wasn't
working right
a staggering 40 000 fmri studies were
potentially used use the software that
he tested and could be made very easily
to show positive results when
non-existent this was on the heels of a
year prior when a separate study
failed to replicate 50 percent of the
published studies in psychology that
they examined
obviously i'm not accusing all the
scientists involved in malpractice
but the drive to find a positive result
is a strong one and what the science is
used for is not always benign
these sorts of studies are used and
abused to advance policy arguments even
in some cases directly in politics with
studies saying things like this
political group shows more activity in
their brain and this part of the brain
than that political group and things
like that
the sheen of science and hard data lends
credibility to these uses and that may
not always be deserved
so this is this year's tour badge cs and
i built it for the tour project it's a
mini polygraph with two channels
galvanic skin response and heart rate
someone on twitter said how can you sell
this without warning people that
polygraph is [ __ ] well
i'm here giving the stock so
you've been warned it's [ __ ]
so about the polygraph
here's some stuff you probably already
know it's rolled into missile in court
which is unlike the rorschach test which
is apparently still mostly admissible it
measures several body bodily parameters
that in theory are correlated with
stress the apa among other groups say
there's little evidence that polygraph
can accurately detect lies
the inventors of the polygraph are more
interesting than the machine itself
nard is on the left his name was leonard
keeler but he preferred being called
nard he was into stage magic on the
right is john larson he was the first
cop in the u.s ever to hold a phd which
he got in physiology
in 1921 these guys work together to
invent the polygraph it's a fitting
invention a stage musician and someone
with a phd in medical field both become
cops and invent the thing that's the
intersection of all those things
it is interesting to note that the
john larson there he's he said later on
that he regretted ever inventing the
polygraph that it was it was abused for
in ways that he never intended
originally
so here are the major categories of
testing the use of the polygraph the
relevant irrelevant control question
tests guilty knowledge so speak of
tension test
they all have some traits in common they
all mostly work because the subject
believes that they work
it's the main job of the examiner to
convince the subject that they work
all of the tests are biased against the
innocent we'll talk more about that
later
and for in the results for the most part
involve subjective judgment
the oldest and simplest test is probably
the conception the lay public has for
how polygraph works some irrelevant
questions are asked and they're known to
be irrelevant by the examiner and the
subject
then the relevant questions are asked
this version has the most subjective
interpretation of the results
it varied so much from examiner to
examiner that it was impossible to
compare anything
this version of the test is really
rarely used today
the control question test this is the
big one in the us and has been for a
long time this one works in a slightly
more nuanced way the pre-interview is
conducted where the examiner goes over
every question with the subject
the questions might be something like
what is your name
have you ever stolen anything
were you at home on the night of the
bank robbery
examiner will say
the what is your name question is the
control question but it's not the
control question it's an irrelevant
question the true control question is
have you ever stolen anything
you may confess to a few things like
stealing pens from work or candy bar
when you were a kid or whatever it
doesn't really matter how much you
confess
so then during the test they changed the
question slightly to other than what
you've already told me have you ever
stolen anything
the premise is that it's impossible to
fully confess to the question it's a
probable lie question one that forces
you into lying even if you don't intend
to
the probable lie questions establish the
baseline for what a lie looks like
for that person
on the graph
the problem with this is that the
cleaner your conscience is the more
likely you are to fail the test
i read an example where this was used
where this particular question was used
as the probable lie question
and here it is other than what you've
told me have you ever done any illegal
drugs even once
the subject failed the polygraph because
they were a super straight edge person
who could with great confidence answer
that that question
which set their live baseline really low
that's just one way the test is biased
against the innocent
the stem test mentioned here on the
slide is just more theater the examiner
instructs the subject to lie on a
question and that they tell the subject
that that's establishing the baseline
but it really isn't
we all know at this point that that's
going to be treated as an irrelevant
question
the probable i questions of the real
baseline the subject answers and then
the examiner says um yeah yeah look look
you can see here this this machine can
tell you're lying but it's all theater
to convince the subject that the machine
works
so that that's the stim test
so is there anything better is there a
better methodology
yeah but only slightly so
in japan they use a test called the
guilty knowledge test in this test often
the examiner isn't even aware of the
facts of the case on purpose
is much less involved in the process the
examiner may still use some theater to
convince the subject of the validity of
the test but
questions are all multiple choice
the subject is presented with the
question and answers
which includes the correct answer that's
a fact of the crime
that's unknown to the public and several
innocent several incorrect answers
the idea is that the subject will show a
greater response when the correct choice
is presented and that this response will
correlate over a large number of
questions
this test is still biased against the
innocent since the guilty can seek out
knowledge on how the test works and
ensure that their response is less to
the correct answer than it is to the
other answers
then the guilty know what the correct
answers are after all
related to the guilty knowledge test is
the peak of tension test this is often
used with sequential quantities such as
was the amount stolen one two three or
four thousand
the idea is that the tension builds up
as the correct as the correct answer is
approached and then we'll release once
it's surpassed so what goes up must come
down
so that's it for the polygraph
this is far from a complete discussion
on the topic in the short talk but it
should give you some idea of the
deception that underlies the machine
itself
on this slide i put some honorable
mentions
you may or may not recognize the machine
on the left it's a scientology e-meter
the glorified love tester that tells you
about your uh painful emotion engrams
and the invisible aliens that are
attached to you
and on the right is d.d palmer the
founder of chiropractic that's another
field where the technology is used to
give a sheen of credibility
to the underlying pseudoscience
so the next time you're using an
electronic tool question if you're being
deceived either by someone else or by
yourself
i'm giggs and you can probably find me
in the hardware acting village if you
want to discuss
enjoy the rest of defcon
and i apologize for the
bug zapper
lots of moths tonight
you