PUKINGMONKEY: I am "Pukingmonkey" and we are going
to talk about how your car is tracked today.
Originally I noticed license plate readers a few years ago.
I didn't know what they were, then I did.
I build a detector, so when my toll booth thing was "red"
it notified me.
Then I noticed other ways we are tracked with smart phones
and even "dumb" phones.
I tracked down, you have the right to travel.
You have the right to travel anonymously.
And, generally, it's yes, it's if you're driving,
because you have licensed.
Taking a commercial flight, as we all know, to get here, or crossing
an international border.
Otherwise you do not need to have ID.
License plate readers if you are not familiar
with them basically are an OCRs on steroids.
They use infrared and optical to find the license plate, do an OCR on it,
track it where it's been found through GPS and coordinates.
And if you get enough data points, they can track you whenever
you've been.
Here is some pictures of some New York City license
plate readers.
New York City tends to use a company called L Sag North America.
You can see the back of the car, the one on the left is an older model,
the one that's larger is a medium model, it's not the newest.
You can see how they're mounted to aim toward license plates.
And you can just see back on the back of it, this
is actually another jurisdiction, this is by federal PIPs system
and you can see it's under the light bar, there are three of them, left, right,
and side.
And that's L Sag's newest model and if you look at most of these
they look like they have get the other one.
They look like they have this is the old model.
Which has two cameras in it.
There is a visible light and infrared light camera and April bank
of infrared LEDs and on the back of it says "do not look at this"
the infrared LED radiation.
The new one ASP on the light bar and looks like it has
a single camera so I haven't figured out if it's it's probably just IR.
If you get it just right you can see on the back the nice, red glow
of the infrared LEDs and they pulse say the.
These are fixed cameras at 40 Wall Street the Trump building
on Broadway and that's the same three cameras
at night that you can see the glow.
When I told people I found these cameras,
they say "I see them everywhere and they're not" these are traffic control
cameras, look for your car instead of the loop in the ground,
to change the lights.
These are not license plate readers, either, these are red light cameras,
what's the big deal with capturing the license plate information,
they have time, location, and they keep it forever.
New York City keeps it five years, Jersey keeps it five years,
and I couldn't find data points for anything lower than 2009 where
they had 108 fixed and 130 mobiles and I'm sure this number has not gone
down and it's impossible to opt out.
As you drive by you get read.
So is it legal to do this tracking.
Turns out it is, because there is no reasonable expectation
of privacy of your license plate in public and these are the cases
of why it is and people say, I heard that you can't GPS track my car
without a warrant but that's different
because the warrant was needed to put the GPS on the vehicle, not
to actually track it.
And the other question was they said
they couldn't use infrared technology to look into my house and that
is true but those are constitutionally protected areas and your car
on a public street is not a constitutionally protected area.
So FEMA has been funding this to local police departments
for the last couple of years, 100% cost of the license plate readers
has been coming from FEMA.
This is a grant to Vermont for $6.6 million.
This is the Vermont side of it saying, yes, we will use 100%
of the proceedings from this to fund license plate readers and this
is Burlington, Vermont, they purchased two
for I know you can't read it, for $45,000 for two.
So the retention data New Hampshire has a general ban on this, people
of New Hampshire said no, which is great.
I hear they're trying to ban them in Montana, working on that.
Maine has a lot of these.
You cannot store this data for more than 21 days in Maine
if there is no criminal investigation.
In New Jersey they must retain all data for five years and
after five years it must be destroyed.
Not sure how that works, I guess they don't have back ups.
New York City retains it for five years even though
they have video cam remarks video feeds, after 21 days if there
is no crime involved in a video feed they claim
they destroy the videos but they will keep
the license plate data for five years.
Now they have this data, and it's actually public data.
Minneapolis released the data to the public and recant and I'll show
you that later.
It can be discoverable because it's data about you.
Generally if there is an investigation about you,
you can ask to see what the police have on you,
in New York it's called "Rosario" and it's statement by them, and
the police department has claimed this is not a statement
but you cannot use it to discover it so they're using it
investigate you but it's not a statement so you do not get it
from them to see what they are investigating about you.
And Minneapolis, the first column is the license plate number and the text,
the time and the GPS coordinates with a picture of the license plate
and the back of the car.
They have fixed ones, too, and this is how they redacted it so you cannot
find where their fixed license plate readers were.
You can just look for them.
It may not matter if there is retention or not because there
is a commercial market for this there is a company F company called Vigilant
Solutions and their sole customer is law enforcement and tow operators
use this to find cars to be repo 'ed and law enforcement will buy it
whether they have it retained or not and you can buy it from TLO.com
for $10 a pop and you put in a license plate number and
they will tell you where it has been seen.
They say they have 1 pill I don't know data points, TLO.
This is not law enforcement, this is one of the cars from Vigilant and
they have their own license plate reader and it's infrared.
I went about building my own and it's hard to avoid them
because there is a lot of them, but at least you know there
and because they're always on.
I had a lot of failures, full sunlight, I have my detector,
I'm detecting my remote control from 80 feet and I can't detect
the reader but I had to use optical filters,
the LEDs they're using are not standard that you find in remote controls,
they're near IR, 755 nanometers, and the filter blocks everything
below 720 nano meters and you can see it glows but there
is ambient IR there and I got another filter that was 30 and you can see it
shines right through so I use that to do it and this
is why I'll describe this graph.
The magenta is the standard infrared detector that
you would find in commercial stuff, the bright red is the wave length
of where the L Sag North America you can see
I put up where the visible was and it's just above the red and
the green is the filter and the black line is the detection
of I bought a wide range photo diode, and the detector looks like this,
and I will be at the hardware hacking village today
and go over the full specs of this.
That's the detector with the filter on it.
I super glued it on to it and put it into the little old DSL splitter case,
put LEDs on it and this is the proof of concept.
(Noise!
) (Away from microphone.) Actually what it's
doing in the IR is not pulsating it's ramping
up from zero to full because they're trying to get
the best exposure of the plate.
It look to us like it ends up looking like a 3 Hertz frequency on it.
So eventually it turned into this, because I tried
to prevent false positives so anything between 3 and 9 Hertz will set it
off and I use the monkey to tell me I got red and these are
the same 3 and you can see in the next video where it is, there
is a TGIF's on the right and scaffolding and it's right before the light
but you get red near the TGIF's because it's angled.
(Noise) There is the scaffolding on the right and the monkey screams!
(Laughter.) (Applause.) Is there anything you can do
about your license plate being read?
There are things you can.
Steve Jobs never had plates on his car.
California had a law that you did not have
to have a plate for six months, that's now been changed to 90 days
but he got the same car over and over so he got a new car and
he never had plates so if you have enough money you don't
need plates in California.
So maybe will he will he can help us, these are
the guys that are running these devices and I found personal vehicles
of police I blocked their license plate numbers not for their protection
but for mine.
This guy most of them are near police stations and
they usually have tinted windows, they usually don't have inspection
stickers, parked illegally, so they're easy to find.
This guy doesn't have front plates he has a cover
on his license plate that's dark, another illegal thing and you can see
all except his windshield he has a PBA shield in his windshield that
is not although indicative of a cop put this guy is and
the windows are illegally tinted.
This guy has the things that shift on the back and I know he's
a cop because he's tinted up and parked in an MTA police only,
otherwise he has a lot of balls!
(Laughter.) This is the front and back.
You can never get the full license plate number you would
have to put it together.
This guy is tinted, no front plate, back is there and I know it's
a cop because he's standing next to the car.
(Laughter.) I like this one.
You can see the police car in the background but I only
like this because he didn't care about his front plate he cared
about the back more and he has "EFF" plates, I don't think
he knows what that is!
(Chuckles.) This was a uniformed officer making
a right turn I captured and he's driving with his tail gate down and
he has a piece of wood preventing whatever
is in the back from rolling out, and he has stickers that says New Jersey
state police and "hero" and I find out that's common.
You can see him standing near the car in the top photo,
he has occasion (Cutting out.
) Front plate and even his windshield is tinted black.
He has his tail gate down, too, so you can't read it.
Maybe he's just parked there because the other guy was driving,
this guy was parked, maybe he's getting something out,
few days later, I found it different spot, tail gate down, same car.
Another one, it's illegally parked completely black no
inspection sticker, no front plate and he, as well, has a darker cover
on his back plate.
This was the one that scared me
because he came out as I was taking the picture and
he said "what are you doing?"
And I said "this car is absolutely beautiful I love it!"
I'm glad it was a nice car and not a piece of crap!
Thin blue line, front plate, completely black ended windows,
windshield, and PBA license plates and (Away
from microphone.) has a black shield over the back plate.
What these cops do is typical, what I just said but you can't do any
of this, this will get you pulled over in most jurisdictions.
They can do it because no cop is going to give them a ticket,
they're going to get professional courtesy.
You can try and do temp tags but you run
out of time and they're not always great because New York temp tags are not
good in Massachusetts, they will impound your car
as unregistered and uninsured, and then you have to tow it home.
They tend the registrations tend to be one use numbers.
I ran across these temp tags, I have no idea they have
an expiration date there is no number and it seems to be
from a company.
Or maybe they just don't care.
Or maybe it's Georgia doesn't care, because it's
from Georgia so you get 90 days and most people can't go through there.
You can get commercial plates so they aren't registered
to you and there are problems with commercial plates
because in New York commercial vehicles have
a different rule set than vehicles and you can see, police check point,
all commercial vehicles must stop and they look inside each struck this
is not just to check documents.
Since it's not usually theirs, they comply, sure you want to look
in the back of my truck, go ahead, they want to get their job done.
The other things that are hard for the LPR,
North Carolina took a bunch of plates and ran 'em
through to see what LPRs had difficulty reading.
If you have a nonreflective plate it's invisible
at night and it's difficult during the day.
Nonrefrequent active plates are uncommon now.
If you decide you can remove the reflectivity but it's a crime
in California to do this and if you're in Massachusetts you
will fail inspection and you have to get a new plate and go through.
Low contrast plates, the color of the letter is close to the color
of the background, red characters it tends
to have trouble with and if you have three or more stacked
characters because they tend to be small it tends to miss those and
if you put registration stickers like Missouri I think puts it right
in the middle of the plate near the letters and that tends
to screw it up, too, so they have trouble with that.
8 digits or more, narrow letters are not great and great
if you have a front plate, only read half the time.
These are the states that have the greens are
the states that have one plate, red will have Nevada is special
because they have there are rules for it.
And these are the states with legal, nonreflective plates that are still valid,
not very many.
You can try manufacturer plates but this is the date
of the youngest car you can have, for California it's you would only going
to 1962, so that doesn't work, either.
See a lot of obscure plates, people using
whether they're doing this on purpose or not is unknown
to me but this causes problems.
You get salt spreaders, plows, monkeys, tail gates,
I'm not sure what the front of one of those is but the bicycle things make
it impossible to get a read but these are all these can
all get you a citation, they tend to be not moving violations,
obscure plates, it's a $100 fine, no court appearance, you pay it
and move on.
Or you can get some plates that is not your number.
This is the University of Michigan plates
but the it leading "M" on both of those is not part
of the registration number.
They can still get you because they have a full number, it
will be figured out eventually.
You can do bumper guards if you're parked
because they read 'em when you're parked they ride
down the street reading the plates.
More bumper guards but don't drive I have seen people
driving down the road with that covered, and
the other worry is if you have no plates on your car,
every jurisdiction no plates cars are abandoned and subject to confiscation.
You can legally if you have Easy Pass
in your jurisdiction you can usually legally obscure your front plate
and there is a law for it and there is one exception and that's
for the external EZ Pass reader.
Don't do this, these are government documents
and you will be charged with tampering.
So I built a camera to see what the license plate readers are seeing
but most commercial infrared cameras are 850 so I bought
the 750 nanometers LEDs to see what shows up with that and
the 735 LEDs, the 420 guys like this for grow lights so I'm
on some other list now too!
(Laughter.) You can buy these things that say "hey,
no red light camera" put this on the back, it's clear, it blocks
above 850 nano meters but since the license plate reader
is below that, the first one it's regular, this is the middle one
is with the 730 and if it's 850, these kinda work
but they're illegal as well.
You can see what they do on other plates.
I ran across this by accident using the camera on plates
during the wintertime since I'm from a place that salts their roads
and this is a license plate with a whole bunch of salt on it.
Visually it doesn't look too much different on the top, this
is with the flash and that's with the IR.
That's a moderate amount of salt because it looks
like the salt absorbs enough of the IR to make it unreadable and that's
with "a lot" of salt.
I don't want to go through those.
You can get these are states that have stacked characters, you want
the one like New York that has NYPD makes it
difficult to read, the Jerseys once aren't great,
easy to detect.
You can get special characters that are hearts and ampersands,
and they're sometimes IPR'd, and some states have those.
You can change your plates as much as possible so it won't avoid detections
and you won't have that big of a history.
In Florida it's country by country but one
of them I think it was Mississippi it's $1.25, you can change your plates
every day at lunch.
(Laughter.) If it weren't for the DMV taking four hours.
Manufacture them are reasonably priced.
These are the states with the eight character plates,
not very much and that's it for the license plate reader.
Then I moved on to the EZ Pass, electronic toll collection tags,
most people forget they're in the windshield and it's
at 915 megahertz and most of them don't have batteries anymore,
I took mine apart, has a nice battery, has a switch and figured
out the current draw of when it was being read and not,
you shouldn't do this because it's not your property,
you have to return these and I basically built a low side voltage detects
and when it went off it would setoff the timer and make the cow moo.
The circuit integrated into it, put an on and off switch
on it so I can turn it off while I'm driving and drove
around and found where it got read.
This place, there is no tolls here, but it would go
off underneath the sign so I stopped on the side of the road
and looked backwards and it may not be on purposes
but you can sigh there are two readers behind the sign, white boxes there.
These aren't hidden, they're just out there.
This is the access to the Lincoln Tunnel
from the Jersey side.
If you're up top, you're committed to going through the tunnel to pay
the toll, and there are three here and you can see
the one that reads you but it's not going to charge you the toll.
You will get charged the toll at the toll and you will get read
at the entrance of the tunnel.
And they want to know, because this is the last exit, there is one
at the exit for the last exit in Jersey, so it's being watched.
You drive around New York City and you
will see them hanging from lights.
And I made it easy to see, another one.
I got tired of taking pictures of them.
These are from a company called Trans Core.
They can read all the protocols including EZ Pass
which was a closed protocol until a few months ago and
they had it reversed engineered, and it will read the Sun Pass
from Florida and that's why New York City likes it,
they get everybody.
I didn't like I had to be detected, it was like a ping, so for me to find
out if I was being read I had to give my position away
as well so I got a 915 megahertz radio and put it
in a tin with a little meter on it and we'll do a proof
of concept here, the Adrena One is in the cow on the left and the one
on the right I built.
(Noise.
) (Cow mooing.) And right under the sign, as predicted, it gets red.
We will go through the Holland Tunnel again,
maybe we will do that again, to show an EZ Pass works just fine.
(Applause.) On the first one I showed you I circled
the tag and the cow on the bottom is already going off.
I did a rundown 7th avenue from 44th Street Time Square area
to Madison Square garden and you will see how often it gets read.
It's going already.
It moos only a couple of times but as long as the nose
is on it's being read.
This is a 5 minute journey, so it's being sped up.
Still on.
(Mooing, mooing, mooing) (More mooing!
) I'm in traffic.
(Mooing, mooing) (Mooing, mooing) (Mooing, mooing,
mooing) It goes off as soon as you pass 31st street and remains
off until the Lincoln Tunnel, which is not a toll, and this is exiting
from Manhattan at the Lincoln Tunnel.
(Mooing, mooing, mooing) The New York state
Department of Transportation admits
they do read your easy pass but I didn't expect it
at every intersection.
They say they do this for travel times.
I have never seen travel times in the middle of Manhattan!
(Chuckles.) What do they do with this data?
Do they retain it give it to the NSA, the "New York Times" said they did!
(Chuckles.) This is easy, if you have these things you put it
in the antistatic thing they gave you, it can't be read or if you have
a sticker you're going to have to build the cage
around and it I got that idea from the car rental company
they have these fold down things so you can pop it
up and it won't be read, but if you do that, it gets read
before the toll, at the toll and after the toll so if you're doing that,
you're not showing up at these other places you may be
a person of interest.
If you're only seen at the toll.
Then we come to your tires.
Back in 2000 Firestone had a strike and replacement workers made their
tires and they tended to blow up.
Something got passed called "Tread" and they wanted toe track who made
the tires because there was never any there
is no serial number on tires, they're molded, the mold
from 10 years ago is the same as today so you can't tell when it
got made.
So there are a couple of things in your wheels.
First one is the tire pressure monitoring system that's not
in the tire that's part of your rim on the backside of the valve stem.
This transmits at 315 megahertz and it's unique per rim.
This is not so bad because to get your ID somebody has
to some to your car and get the ID, but they could.
Then the tire manufacturers are putting RIFDs in the sidewalls themselves.
There is a unique serial number in each, Michelin uses 915 megahertz,
Good Year could not get that to work, if you get your tires from Ford,
Chrysler, they put the VIN number in the tire so now
the VIN number that goes to your state I know
of no one that's doing it but if I were somebody that wanted
to track I would be putting sensors at sides of roads and this
is a tire pressure monitoring system.
This was a picture showing a run flat tire and you can see where
they cut away the run flat it's a transmitter, it's
like the EZ Pass, has a circuitry, battery in it.
You can't take your tires off and put them back
on yourself you need somebody else to do that and
if you disable your tire pressure monitoring system you
will have that light on the your dashboard
the entire time and if you have an automobile inspection you probably
won't pass it because in Jersey if you have an indicator light on,
check engine, low tire pressure, seat belt indicator does not work you
will not pass inspection.
You might want to try and jam it.
I was unsuccessful at doing that, that's for later.
You can try an EMP pulse that maybe the chip
is in the sidewall of the tires but rubber absorbs RF very well.
There are other RFD things around, parking passes, hang tags,
you can get a radio to see if that's what happens if it's
a hang tag and something opens a gate for you it's probably an RFID.
There is a community that used their parking permits
because they had so much counter fit parking stickers for the street
they put RFIDs in them and put them on the cars you want to park
on the street you're going to be detected, too, it's tough
to get around it.
Italy is doing this and Texas was going to put them in their inspection stickers
but I don't know if that passed.
So you need to not use those if you can.
I came across a company called Inrix and they collect position data
from 100 million devices.
Google maps uses them for their traffic flow, six
of the auto manufacturers with built in nav uses Inrix, 8 out of 12
in the top navigation apps in the iStore use these people, and
they track dumb phones with contracts
with the cell phone companies.
And they originally started by tracking commercial truck fleets.
So they have lots of data on you.
If you use any of these apps, you've giving it to them and
they know who you are.
So at the end of the day, you need to assault your plate, bag your tag,
jam your tires, turn off all electronic devices.
And that's it!
(Applause.) I will take questions if you have them.
AUDIENCE MEMBER: (Away from microphone.) Lighting
the back of the car with LEDs you can do that to block it,
you're going to need both of them but many states have if you jam
a red light camera you have committed a crime.
AUDIENCE MEMBER: (Away from microphone.) The back
of the lights, no, it's usually open worded saying
if you can defeat a red light camera any means any way
you have committed a crime.
So they're illegal and if I was the LPR guys and you think you have IR
and you used 850, if I was L Sag I would put
the same blocker you put on your plate to block that
and I won't see your LEDs because 740s are uncommon.
Wait, it's coming.
AUDIENCE MEMBER: You stated the toll collection is shared with NSA.
Does that apply to LPRs?
I don't know that.
The only reason I know it was shared is because "New York Times" said
in one of the articles written after Snowden that
they get EZ Pass data, most people think it's at the tows,
big deal, but it's much more than that, but it tend to be government data
and since FEMA is fund it's part of their
for this money we want your data, too.
I have no documents saying that.
AUDIENCE MEMBER: How about Frisnel lenses
or dust covers PUKINGMONKEY: All these things every jurisdiction has
an obscure plate law so if you obscure your plate AUDIENCE
MEMBER: (Away from microphone.)
PUKINGMONKEY: To depends on the jurisdiction.
Most of 'em like if the red light camera can't get one of them is Pennsylvania,
that's the one I knew well because basically it's broad: Anything
you do to defeat a red light camera is illegal.
It's a misdemeanor but it's more than a moving violation;
it's a crime.
That would fall under that.
I think California has the same law, too, but don't quote me on that.
I read a lot of state laws and they all start with to blur together.
I would suggest you check your sources
on the "New York Times" article as far as the availability
of the toll tag reader ID to NSA.
I know the people who built the system.
PUKINGMONKEY: Yeah.
We don't keep any of that data.
PUKINGMONKEY: Is that New York City DOT?
Yes, along with the system the DOT, the last thing they want to know
is who the hell is driving that car.
PUKINGMONKEY: But they said EZ Pass data
if it was actually All toll tag datas are scrubbed, so double check
the source on the "New York Times" and also
with the Inrix data, you might want to double check that source, too,
because I challenge you to find anyone
at Inrix that can pinpoint a vehicle.
PUKINGMONKEY: I'm not saying they can't.
All I'm letting you know is you are being tracked, at this point.
AUDIENCE MEMBER: You're being tracked on your Android phone,
but I think Google has a better chance
of identifying you than Inrix.
AUDIENCE MEMBER: (Away from microphone.) (Applause.)
Where do you want to go?
(Laughter.) AUDIENCE MEMBER: I was wondering
if you've done any experiments with putting, like, a coat
of clear coat paint over a layer of salt to stabilize it so it doesn't watch off?
PUKINGMONKEY: No, I actually want it to wash
off because let's say you have to go through a car inspection.
You have to wash it off but these are up to I'm not saying to do any of this,
actually, this is just ideas.
(Laughter.) These are just ideas!
AUDIENCE MEMBER: (Away from microphone.)
PUKINGMONKEY: I'm not sure how they detect if it's reflective or not, right,
because it's a laser beam that says if I get enough back it's fine, at a corner,
all I know is that is part of their inspection
criteria, Massachusetts.
AUDIENCE MEMBER: Is there any state law that says you must keep your
license plate clean?
PUKINGMONKEY: It's the same as the obscured plate law.
You cannot put mud or stuff on it.
Typically it has to be visible and that's why I liked the salt
because visibly it doesn't look like it, and in states that have winters it's
kinda common to have salted plates, not probably very common out here.
AUDIENCE MEMBER: My question is how did you salt your plates
to maintain deniability.
PUKINGMONKEY: Water, salt, super saturated, pour on the plate,
off the car, let it dry.
AUDIENCE MEMBER: Thanks for speaking with us.
I had a quick question about the data and how it's available.
If we can contact our local counties and get this information for free?
As far as when our plates were read?
PUKINGMONKEY: I don't know how they typically will not give this data out.
Minneapolis is the only one I know.
They did it briefly and then recanted and said we're not going
to provide this anymore, so I know of no one that is proving it to people,
but the company, TLO.com, you can purchase that,
but it's privately collected data, which there is no laws
against any of that.
AUDIENCE MEMBER: Thank you.
AUDIENCE MEMBER: You put effort into investigating state by state
the rules for changing license plates
and I appreciate that but what is the perceived advantage?
PUKINGMONKEY: You have less of a history.
You can still if people have a routine that's every day
of the week you're detected very quickly, but they could go back
and say, well, he's only done this for a week
if you change your plates every week.
But they also have all your previous plates
but I don't think that's a common practice
to change your plates a lot so they might not say, let's go back
and look for all his old plates but it would be trivial to do that query,
here is his ten plates, run 'em all.
AUDIENCE MEMBER: Do you know of any paint that you can use
on the infrared spectrum that would be transparent on the visible spectrum?
PUKINGMONKEY: Myth busters did this and busted it so I didn't go
down that road.
They said they had a bunch of things for a red light camera,
some sort of spray that did not work
and I saw it advertised, I did not purchase it or try it.
That's usually for speeders trying to avoid laser detectors.
AUDIENCE MEMBER: A lot of questions focused on trying
to prevent reading of your plate and as you mentioned every state has
an obscured license plate law, what about a different approach,
feed it go bad data, lots and lots of bad data.
PUKINGMONKEY: That's one of the things the detector is trying
to find your plate so if you get reflective material
about nonreflective numbers on it, it will probably find your plate
and read the other bad data along with it so you
will still probably be captured, but as well as your bumper sticker,
that you tried to say semi colon 1 equals 1 to try
to dump on it, but you gotta do that in, like, eight characters.
AUDIENCE MEMBER: My questions is about sanding down license plates.
I have a bunch of people in Arizona that sand 'em down,
everything around the numbers.
What's that about?
PUKINGMONKEY: Sanding the plate will remove the reflectivity.
AUDIENCE MEMBER: (Away from microphone.)
PUKINGMONKEY: Yeah, it has the numbers though on it, right?
Visibly.
One of the ways detectors are looking to find it on the back of the car, one
of the ways it does that is by reflectivity.