I'm Bob Wilhelm, Vice Chancellor for Research and Economic Development and I want to thank you for joining us today for the eighth Nebraska lecture in the N150 series. This is a part of the university's 150th anniversary celebration. The goal of the Chancellor's distinguished lecture series is to bring together both the university community but also the broader Lincoln community and beyond to complete to celebrate the intellectual work that takes place here at the University of Nebraska-Lincoln. The presentations highlight our faculty's excellence in interdisciplinary research and creative activity. The lecture series is sponsored by the UNL Research Council in cooperation with the Office of the Chancellor, the Office of Research and Economic Development, and the Osher Lifelong Learning Institute known as ALI and I want to make a special welcome to ALI members that are here today. Let's give also some special thanks to the humanities Nebraska and its executive director Chris Sumerich for helping sponsor this year's lectures. Thanks also to the National Endowment for the Humanities which is supporting the expanded lecture series. We have 12 lectures this year, generally we have two during the year. They're supporting this expanded series through a grant and with the support we're creating a podcast of the presentation of each of the presentations so they'll be available for people to look back on in days ahead and also to engage new audiences. The University's Research Council is front and center in terms of this lecture series. They choose faculty from a broad range of disciplines at Nebraska to deliver the different lectures. So they look at nominations and then on the basis of both major research accomplishments and the lecture's ability to explain his or her work. No pressure here Dan. They make a selection and this is considered to be one of the highest recognitions that the council can be so on an individual faculty member. I also want to welcome people that are watching this on our live web stream and through Facebook live and then just to get moving here but before we do I'll say something about the format. So after the lecture Deb Hamernick who's here associate vice chancellor for research will moderate a question and answers session with the audience and then following the Q&A will announce a winner of our N-150 book giveaway. So one lucky winner will be chosen from the crowd. We've got a special selection process you'll enjoy and you have to be present to win so you need to stay till the end of the lecture to receive your prize. So also everyone's going to be a winner today as you exit the lecture will be will also be offering ice cream from the UNL dairy store and I encourage you to mingle talk with the speaker have a little bit of fun at the end of the lecture. So now I want to welcome a chance for Ronnie Green who will introduce our speaker. Well thank you very much Bob it's great to be at another Nebraska N-150 lecture as Bob said. We expanded the normal two Nebraska lectures that we have per year to 12 this year so this is our ninth one of the lectures in the series that have covered a lot of the various histories associated with the University and today you're in for a real treat and studying the history of physics at Nebraska in particular. It's kind of also a special deal because there aren't very many people that have had this distinction but Dan is one of them in that he is a second time Nebraska lecturer. He gave his first Nebraska lecture in 2015 when he presented on what the heck is a Higgs boson which showcased UNL's work on the international stage to understand the God particle and in quantum physics. So a second time around for Dan in this prestigious honor and it's also really special I'm sure he's going to do this but I'm going to call it out as well that his dad is here and his stepmother is here from Cedar Rapids Ohio so you bring your own peanut gallery here on the front row so welcome to Nebraska and glad to see you here as well. I'm delighted that Dan's returning to share his insight today on the long and storied history of the University's physics program. DeWitt Bristol Brace is the scholar who changed physics instruction as we know it adding courses hiring instructors and creating laboratories. He also advocated for expanding the campus footprint for physics. Brace Hall completed in 1906 is named in honor of him. More than a century later a renovation to Brace Hall was completed as you'll remember just in recent years extending his legacy to another generation of Nebraska physics students. Brace was a formidable researcher while at Nebraska which is fitting because the Department of Physics I look out and see a number of our faculty here is known on the university as being a leading department on our campus and internationally in physics. He was known for his exacting experience and innovative lab instruments. In today's lecture Dan will share how Brace's research became a cornerstone of Albert Einstein's theory of relativity. Please join me in welcoming Dan Claes our chairman of the Department of Physics the University of Nebraska. Thank you Ronnie. Thank you Bob. I also want to thank Tim Gay who first made the suggestion of the topic as a suitable N-150 presentation. If there's only one face and name on my cover slide with instant recognition I hope to introduce you to the other and draw the lines that connect the two. And although Brace invented three optical instruments his spectrophotometer was adopted by lots of observational astronomers. He held two patents. He amassed a publication list of 20. In addition to the 24 that his graduate students authored while they were working in his lab I'm only going to be talking about two highlighting two seminal experiments that were performed by Brace. Should any of you be interested in much more about the early history of the Department of Physics and astronomy I point you to my own primary source and that was science at the American frontier a biography of DeWitt Bristol Brace with David K and a University of Nebraska history professor whose specialty is the history of science and UNL physics professor from 1965 to 93 the late Gene Rudd who passed away in 2014. The mid to late 1800s were clearly an important period to the fledgling University of Nebraska but it's also a period of enormous significance and astonishing discovery in the field of physics. Early that century Thomas Young a British physician in polymath presented definitive proof that life is in that light is in fact a wave. By passing a beam of sunlight in a darkened room and passing it through cardstock with little apertures that he had etched into it he was able to cast images his artwork representing what he saw in the upper right-hand corner probably a little unclear of what he described as patterns of fringes of light. The photograph below available to us now is a lot more vivid. Young had reason that if light were in fact a wave then like sound or water waves they should diffract as they pass through narrow apertures. They should make patterns as they ripple through one another creating isolated disturbances of enhanced crests and deep troughs where they overlap and areas that wash out where trough meets crest. Interference of light through such aperture he showed give us exactly those kind of patterns. This laser light passing through this slide that has two very narrow slits carved through it is producing that pattern that you see here. Bright fringes interrupted and separated by dark patches. By the middle of the century physicists were already designing apparatus for actually measuring the speed of light. You know if you could pass the shaft of sunlight across the room and time how long it took to move from one marked position to another you'd know the speed of light. You just divide the distance by the time. The time it takes to cross the room is pretty short. You can raise it by reflecting it back so you double that distance. You calculate the speed now by twice the distance d divided by time and that might help. Imagine reflecting it once more into a sighting telescope of viewfinder. Trying to do that of course you have to be very careful with the alignment of the mirrors if you hope to fall into the eyepiece. This beveled mirror allows me to reflect that beam of light across the room and then when it returns down into the viewfinder. And of course everything has to be aligned up just perfectly for you to be able to look through that scope and see the spot of light. But if I set that mirror spinning I'm going to ruin the alignment. In fact as soon as I do we'll have to recognize that it's only brief interrupted bursts of light that race across the room to reach that mirror. And by the time the reflected light returns because the speed of light is so fast that mirror will have rotated and the bottom mirror will be out of alignment. It won't bounce down into the viewfinder. Somewhere else in the room it'll end up. But if I rotate that mirror fast enough I can eventually find a speed where by the time of the first reflected pulse races across the room and returns the whole mirrored system has rotated just enough to bring the next facet into position to provide that reflection straight down. Then the time it takes that one move of the mirror to the next position gives me the time that it takes the beam of light to travel across the room and back. That's how Foucault measured the speed of light and he did it with extraordinary accuracy. He measured it to be 298 million meters per second. Here's the accepted value today. There. Light of course travels through air, travels through water, it travels through even transparent solids like ice and glass. So does sound. But light can go places where sound doesn't. This evacuated bell jar I can still peer through and see things in it even if I no longer can hear sounds generated inside. And of course I guess the fact that light can travel through a vacuum is already evident because we can see sunlight received from the sun through the vacuum of space and stars overhead at night. This raised an important question though of how does light move and in particular how does light move through vacuum.  Air and sound for example. And scientists speculated that even the void of space must be filled with something, something to carry the light. It had to be lighter than air, finer than atoms. And not only did it have to pervade all of space it even had to occupy the space between atoms inside solids. Every time you create a vacuum you can still see light through it. Somehow it instantly fills. It must have already had that ether present. Ether was the name they gave to this ephemeral ethereal substance. And somehow since it fills all space objects are able to move through the ether without impediment. Evidence by the fact that the planets don't ever alter their speed in their race across the heavens. So that's where physics stood as we approach the end of the last century. This is where the University of Nebraska stood. In 1871 it was all housed in a single building and these pictures convey the rough frontier terrain that welcomed new faculty who came to work at the University. By the turn of the century that single building, University Hall, was the centerpiece of a four block campus. There you see in the center dominating the landscape is the old original main building, University Hall. In the foreground to the right that was the second building ever constructed, ever constructed, the chemical laboratory. Physics was originally taught in Old Main. It was taught for a brief time in the chemical, in a floor of the chemical laboratory before it moved to the original Nebraska Hall which is just off in the distance to the right. When they opened with only a total of 70 students there was really only one professor who was teaching science. That was Samuel Augie and he taught practically everything. He taught astronomy, botany, chemistry, I'm just rattling through the alphabet here. Geology, physics and even sections of German and Greek and in fact for the first decade there was a succession of hires, none of which stayed more than one or two or five at most years that were all multitasking in the same way. You'll notice that two hires were made in 82. There were in fact six faculty hired across campus. We had swollen to 284 students by that time. The next year the medical school opened and chemistry enrollment spiked and that necessitated for the first time the hiring of specialized faculty who would exclusively teach in only one area. And I have to thank Mark Group for finding this and sending me this article. Points out in Monday evening, September 12th, 1887. College year opens tomorrow. The examinations for entrance. All candidates should present themselves at the building at 9 a.m. But it talks about the hire of Mrs. Rachel Lloyd, a PhD associate professor of chemistry who got her degree at the University of Zurich at the time the only place a woman could get a PhD in chemistry and hired at the same time DeWitt, Bristol, Brace of Boston. Brace was born just outside of Niagara Falls and he attended Boston University, which at the time shared science resources with MIT. It meant that Brace benefited from attending one of the few U.S. institutions that offered instruction that gave hands-on experiences in the laboratory. He pursued graduate studies at the Johns Hopkins University. At the time America's first true and at that time only research institution and he did it under the direction of Henry Rowland. Henry Rowland had spent a few years working in Berlin in the laboratory of Herman Helmholtz, mourn him in a moment. It's he who did the first experiments that demonstrated that moving electric charge generates magnetic fields. He was most famous, though, for his precision diffraction gratings, which revolutionized optical spectroscopy. He went on to become the inaugural president of the American Physical Society. Now Rowland encouraged all his best students to follow suit and try to find time to go to Berlin and study in Helmholtz lab and Brace took the advice. He studied not only under the direction of Helmholtz but also Gustav Kirchhoff. If you don't know who Herman Helmholtz was, he was the preeminent scientist of that age. He was a physician with broad interests who made contributions in many, many fields. In physics he was known for one of the first treatises that argued the conservation of energy principle and there is in mathematical physics a partial differential equation that bears his name. Anybody who studied electronics knows about Kirchhoff's rules but he actually made contributions in spectroscopy and thermochemistry as well. Brace's selected research topic for his PhD would be exploring a new theoretically proposed property of light. Now light of course bends, changing its direction every time it crosses the boundary from one medium to another, for example as it enters water or glass. We call that bending refraction and it occurs both as you enter the new medium and exit and you'll notice the bending of the light on both sides. But what the heck is happening and how do you explain this phenomena? I've got just this plate with that print but observed through this block of Iceland spar. It's a clear form of calcite. Do you see the double image it produced? In fact watch as I rotate it. The images rotate. What the heck? Clearly the rays of light as they enter this material split into two paths that creates the double image but why? Are there two kinds of light? Christian Huygens noted that if you take a second piece of Iceland spar and I don't have a second piece but I've got a sheet of Polaroid. Polaroid material was originally made, manufactured, bearing little slivers of Icelandic spar in it. It's made differently now but it has the same effect. What happens if I put a second chunk of Icelandic spar above it? I won't split the double image into four images but what I can do is eliminate one or the other depending on how I orient this which offered some clue as to what was going on. Physicist Thomas Young again and Augustine Frenal identified the following characteristic as the thing that made the difference between the kinds of light that were split into the two paths. They said it is the direction of polarization of that wave. A wave is a vibration and I'll send a vibration along this cord. I'm sending this one with a plane of polarization, a vibration that's just going up and down. But you can imagine vibrating this thing horizontally with the ground and having it vibrate left and right. Those are two different planes of vibration and of course I can even vibrate it at some angle if I want. Studying and playing with iceman spar which was a heck of a lot of fun, the following observation had been made. When light is scattered off of flat shiny surfaces, it is polarized. Now auto the light falling down on the tabletop here, it's all randomly oriented so may be polarized vibrating in any plane at all. But as it approaches whatever its orientation is, the surface of the table, what reflects off the table are only those that are vibrating parallel with the surface. That's why I represented it as a vibration that's taking off now in this direction. It has selected among all of the orientations of polarization of the light incident on the table, those in a preferred direction. The way we make polaroid sheets now is with long chain polymers like polyvinyl acetate PVA. Those long molecules act as little antennas for light that is incident upon them. When light falls on these, if it's vibrating with its electric field this way, it can generate electric currents along the length of the molecule and rob some of the energy of the light as it tries to pass through. So light vibrating this way for the most part doesn't make it to the other side. Light that vibrates in any other direction has very little of its energy sucked up because there's much smaller room for currents to flow. But if I've got two samples of the stuff, if I align the molecules together, then whatever light is blocked by the first is blocked by the second, whatever makes it through the first makes it through the second. But if I rotate one at 90 degrees, I block the rest. And if you've got polaroid sunglasses, break them in half because you can do the same sort of test. The reason they work is because if glare is reflected life off of surfaces and is polarized, these polaroids if oriented correctly will block that light out. And you can try it with yours. You can notice that you'll block the glare only at a certain orientation and reflections off the side of the building, you got to turn your head like that to block the glare. And there's how a lens polaroid filter works on a camera. Why the calcite splits the beam this way has something to do with the clearly asymmetric crystal structure it possesses. It is not like table salt, simple cubic crystal forms. Same is true of quartz, another one of the so called birefringent materials, these materials that will split the images of things passing through them. Early that century, William Nicholl had done something very clever. He had taken a sample of ice and spar and he had split the crystal into two halves. So light comes in and splits as it enters and then he slathered on one face Canadian balsam which is a turpentine made from a balsam tree that dries clear. And he used it to cement the other half of the crystal. Because the index of refraction, the degree to which light will be bent as it enters that material, is a number in between the clearly two distinct indices of refraction that define the angles that the two split beams of light travel. It meant that one of the beams strikes the Canadian balsam and experiences total internal reflection just escapes from the crystal and the other one is refracted into and passes through the other side. Clearly the one that shot up this direction must be plain polarized this way, right? And the one that continues forward is polarized like this. In 1815, John Baptiste Biot discovered that that direction of polarization, the direction the light is vibrating as it travels, can be changed. It can be changed by passing through certain materials that can be verified by selecting, with the polaroid rotated into position, selecting a certain orientation of polarization and then analyzing it with a second filter. Remember if they line up, they both pass the same light. If they're at cross purposes, we'll block everything out. The interesting thing is that as the light is passing through this material, can you see that spot of light projected on the screen right here? Sorry, the room isn't dark enough to make that clear. To produce the best effect, ah, there I've rotated and I've blocked it completely so I've eliminated. These are now at cross purposes. But this one is at 9 degrees. This one is at 39 degrees. That's not 90 degrees difference between the two. And that's because the material that we've passed through has rotated. Here is a polar limiter that was purchased by Brace himself when he came here as a new faculty member and trying to understand why that even works is something that Brace was interested in exploring for his thesis topic remember. Already had been demonstrated by Michael Faraday that you could enhance or increase that rotation by applying a magnetic field through the material that passes the light. And in fact you could even take material that was not originally birefringent, turn on the magnetic field and get it to rotate the light. You know, when light falls on a crystal face, if it's randomly oriented it's unlikely to be aligned with any particular crystal direction. But you can also imagine orientations that are. When you're not exactly along any crystal direction, we can still talk about components of that vibration. In the same way that a runner gains yardage by pointing his nose straight down field. He gains none by running to the sidelines to stop the clock, but when he zigs and zags, he's both running down field and across field at the same time. Here I've taken his motion and I've described it as progress down field and motion to the side. These are components of the actual direction that he's moving. If I've got something not vibrating exactly up and down nor exactly left or right, but it's some angle, I can think of it as vibrating up and down at the same time that it's vibrating left and right, like this. I'm going to keep track as these disturbances ripple to the right. Imagine this is a spot on a wall and I'm going to identify the position along its vibration as it tries to work its way up and down by following this little ball as my waves advance to the right. Now notice I've tracked the ball on this little inset picture on the upper left by keeping track of how far left and right has it moved and how far up and down it has moved. If the two wave disturbances, the up and down and left and right, are locked in sync with one another and advance together, notice they approach the peak at the same speed and reach the peak at the same time. So we've reached the extreme of the vibration of that blue arrow indicating the plane of polarization and as it works its way down they pass through the center up and down and center left and right at the same time and then they reach the extreme in the lower left-hand corner together. So a vibration along this direction can be thought of as the simultaneous vibration up and down and left and right as they picked. If the separate components however travel the different speeds and that was Fresnel's suggestion to explain why these rotations happen. If there are directions in the crystal where it's easier for vibrations to advance than others we might split the light into sections of components that don't track one another and lock step anymore. So watch what happens as the wave forms left and right travel in here more sluggishly as the advancing up and down. Notice we've reached the top of the up and down motion but we haven't reached the peak of the left and right motion yet and notice how that's carried us off track from that blue arrow and as we come down we reach we're already on the downside of the up and down motion we're just reached the top of the left and right motion and we see this sort of tracking. What in the world and how do you explain what's going on there? That's what happens if you have to separate out the left and right motion from the up and down motion and it's explained and understood here's what the complete path that I continued to follow it should do it should eventually repeat itself over and over again endlessly. It can be explained by thinking of a vibrational long a plane of polarization a little ball bobbing up and down at the same time as that arrow is rotating. Then notice how the ball moves up and down along the arrow but the arrow keeps changing its position that's how it traces out that figure that I showed before. Now Grace was interested in trying to determine if in fact that's how light moved through materials like that and although he was not the only physicist in the world tackling that problem before the internet it was common for scientists to work in isolation and be oblivious to the work of others. Here's how Grace did it. He took two electromagnets highlighted in blue now with their opposite poles facing and producing a strong magnetic field in the gap between them. There's a hole bored down the center and you can see it on the side view on the right big enough to accommodate two halves of a cylinder of Faraday glass which is just a lead glass that had been split down the center and separated but nestled within as again showed by that side view and then the optics the Nicole prisms and some reflective pieces that separated the two different selected out and separated two different plane polarized beams of light passed them down that aperture one through one half of the prism another through the other combined on the opposite side to produce fringes like I talked about before the interference pattern. Here I've got a beam splitter and a mirror on two sides taking this laser light reflecting some of it to this mirror and allowing some of it to pass forward like in that speed of light measurement that I was talking about some of it reflects back toward the screen and some of it from this direction passes to the screen and I've got two overlapping beams of light now and I'm producing an interference pattern of fringes like we talked about. If you'll follow from O to A to a prime to C or O to B and B prime to C you'll notice both of those path links are identical and each path link carries it through the same length of a sample of exquisitely produced Faraday glass and they're the same because they split from the same sample and so they have the same experience they travel the same distance how they interfere depends of course how the wavelengths of light meet when they finally do. If we energize the magnet then notice there's one sample of the Faraday glass that will enhance the rotation supposedly and change the speed that the other one will carry the light through and if you change the speed of one things as we showed right if that changing speed is what causes the rotation then you will get two beams of light that now when they come together to form an interference pattern start to shift which means the pattern you see will start to shift. An electromagnetic current of 43 amps shifted the interference fringes those fringes you'll notice if I tap it I'm disturbing things and you can see the the fringes will move and breathe in and out. He saw the interference patterns move he turned off the magnet and then reversed the current and saw it saw them move again but in the opposite direction by exactly the same amount and then he repeated the experiment by sliding that piece of Faraday glass into the magnetic field and that one out. He showed that on these two different paths you could control the speed with which the light traveled through the Faraday glass by introducing the magnetic field. He defended his thesis successfully and Helmholtz his mentor lauded the young physicist first of all for his perseverance secondly despite the warnings from Helmholtz himself that he was asking the impossible of the machinists his experimental design would be too hard for anybody to build and then finally he was pleased with the experimental design because it worked. So in 87 Grace came along with Lloyd to the University of Nebraska both of them were promoted to full professors of the following year the same time that the science department split into distinct physics and chemistry departments. Grace spent a decade trying to build that department with more and more professors and swell the enrollment and especially in the graduate program between 99 and 1900 he had a particularly fruitful time together with two collaborating faculty and a handful of graduate students he published 11 papers in prestigious journals. At the time the University of California System physics professors were averaging three maybe four publications a year although at Harvard it was 14. Grace was eventually elected the Vice President of the American Association for the Advancement of Science and for the American Physical Society. I'd like to point out that the very first PhD awarded at the University of Nebraska was to Grace's first graduate student. That was Harold Allen. He actually came from the University of London explicitly because he was interested in working with Grace. He served as an adjunct professor here briefly after he got his PhD before he went on to India where he found his own faculty position that well at the time was one of the best engineering colleges in Asia. By 1905 we had six faculty and two instrument makers for the research projects and most of that contingent was here for this group photograph taken on the steps of Nebraska Hall. But by that time there were less mundane issues that were occupying Grace as well. You know if the luminiferous ether pervaded the vacuum of space how did the earth's motion through it affect what we saw because the earth is moving right? It's rotating once every 24 hours and given its size that means at the equator the surface of the earth is moving 465 meters per second that's about a thousand miles an hour. Okay that's only a millionth of the speed of light but the earth is also moving in orbit around the Sun a hundred times faster. If the speed of a wave is uniform and constant in all directions of a media then you would expect every disturbance will produce a circular or spherical wave shape as evidenced here in these water ripples. That's because everything's moving in all directions at the same speed. You'll notice however if the source of that wave disturbance is moving then the speed of the waves the way the bunching of the waves is different in all directions the shape of the pattern you see. You see in the advance of the object you'll see waves starting to bunch up and in the back they start to spread out which makes it evident at a glance with this water skipper which direction it's actually moving. If the earth and we as riders on it and any source of light like that lamp attached to it are traveling through the ether or if you prefer the ether is rushing past us it'll alter the apparent speed of the light carried through it in the same way that I was just describing with water. If the light source and the observer and the medium that carries the light were all stationary then light would emanate out in perfect concentric spherical disturbances and the recipient of the light would receive it no matter what direction they are from the source at a light speed will cause C. But if the medium were moving past the source and the observer in the direction shown here with the speed V then notice the light that is trying to reach the observer is retarded. It's trying to fight the headwinds of the ether. It will be observed to impinge upon the observer at the reduced speed of C minus V and where we traveling through the ether in the opposite direction we would receive that light faster. C plus V. If we wanted evidence that the earth is moving through an ether and we wanted to know what was the direction and speed of the ether in the universe we could get a sense for that by just analyzing its effect on light. In particular we could for example compare the speed of light at sunrise when the earth is carrying us toward the sun to the speed of light at sunset when we're racing away from the source of light. Or here's an experiment that we could imagine that could take the measurement and compare for many different directions at once. Let's set up a bunch of mirrors equidistant from the source and watch the reflections back to the source. If we were in stationary ether and we weren't moving in the source of light when it wasn't moving then the reflected light should all come return to the source at the same time. But the headwinds of the ether were that present then notice the light that's trying to race toward the mirror to the right will be slowed down to a speed C minus V. And the ray of light we expect to hit the mirror above will miss it because it will be blown to the side and what hits the mirror overhead is a ray of light that had been in advance. This tells us that the time to reach that mirror and the time to reach that mirror wouldn't be the same if the ether were carrying the light and the ether were moving past the earth. In 1887 here's the experiment that proposed to do just that. A thinly silvered glass plate like that one that I had here is a beam splitter that allows light to pass through and be reflected at the same time. If I've gotten mirrors equidistant from that point in the two different directions they'll reflect the light back to that point and if this is and it is the thinly silvered glass plate the one that bounce back from the top will pass straight through going down and the one that returned from the right some of it will be reflected as well. And we can get an interference pattern down there that tells us when the light traveled there and there and there and they met together you know exactly how the two different waves overlapped. What I didn't show you here before was you'll notice as I walk by that thing will go crazy but in fact if I just move my hand close to the light beams without touching you'll notice there's a slight breathing of the pattern. I've altered things just by the warmth of my fingers. If this was aligned to where we anticipate the headwinds of the ether to be then there will be a difference in the amount of time it takes to travel this way as that way. And what the experiment proposed to do was then to rotate the whole device and to make this one the one that faces the headwinds and this one across and look to see if there was a difference. How would that difference manifest itself by changes in the interference pattern? In 1887 that was the year Brace started at Nebraska. Michelson and Morley conducted that experiment. They set up the optics on this foot-thick five-by-five-foot sandstone slab floating on a tub of mercury. That's to isolate it from vibrations. You saw what happened when I walked by. But also to allow them to effortlessly rotate it. They didn't just bounce the light back and forth. They set up mirrors so it actually bounced many times increasing the total path length. Hoping to enhance any difference that they'd observe. Here's their data, the dark connected lines, basically showing nothing but a little bit of scatter from point to point as they took their measurements. But super composed upon the line that was the expected difference they would observe given that the Earth's velocity is known. And you'll notice basically what they saw was they couldn't measure the movement with respect to the ether. But that mean they insisted that perhaps you changed the length the dimensions of your apparatus by rotating it into the headwinds. And so there were two different distances and they'd have to change by this amount. And if they did you would preserve the time it takes to go the different paths so that the fringes wouldn't have to change. But to someone like Brace, that meant that even non-birefringent crystals would get changed and become birefringent. And of course he had the experience to take measurements to check if that were true. Here was Brace's turn of the century lab in Old Nebraska Hall. Here's his work bench where he assembled the experiment. Here's his sketch of that experiment, citing already published work by two other physicists that looked for this effect unsuccessfully. He pointed out errors and weaknesses in their argument and then proposed to conduct an experiment that would be far superior to either of those two. There are two nickel prisms, so effectively doing the job of these polarizers. One of them is selecting a plane of polarization. And the other one to analyze it to see if the direction of polarization has changed after all the reflections. The reflections carried it through a sample of pristine flint glass that he had purchased. And then he introduced two little pieces of optics here, what he called the sensitive strip in the compensator that worked this way. If you look through the eyepiece, the sighting eyepiece, and you see the spot of sunlight through it, if you drop one of the nickel prisms in place, you'll reduce the amount of light that comes through, of course. Then if I drop the other one at right angles to it, I'll eliminate the spot entirely. And then he took a thin sliver of mica and covered half the field of view. And the mica by itself provided a little bit of rotation. So instead of being blocked by the second filter, sunlight snuck through. And then he took another slab of mica across the whole field of view, so you saw basically this. And then he adjusted the nickel prisms until the left and right field of view looked uniform. Now, if he could set up this device, and like the Michelson-Morley thing, rotate it into and out of the headwinds of the expected ether, he could tell if there were any birefringent effects being introduced by suddenly seeing a difference between the left and right field of view to the scope. And calibrating his device, he was certain he could identify a rotation that was as small as two-tenths of a degree. Turned out the instrument he built was a hundred times more sensitive than was necessary to measure the expected effect. And he took his measurements in July and December of 03. And then in February 04, the separation of months so he could compare the earth at different seasons of the year, going in one direction in its orbit, going in the opposite, and six months later. And you know what? He set the device along this heavy beam of wood that was anchored and pivoted between floor and ceiling. That's how he did the rotation. He didn't put it on a sensible slab. He strapped his head in with a headgear so that he wouldn't alter his field of view through the eyepiece, as his assistant rotated the device slowly. And he was watching to see if he needed to make any adjustments to the prisms because there was some change in the light coming through. And he saw nothing. He published that in Philosophical Magazine of Very prestigious journal of the time. Not only did it appear in print there, he was invited to submit basically the same article to Frasztrich Ludwig Boltzmann's commemorative 60th birthday edition of the most important scientific achievements of that year. Other contributors into that volume included Hall, Arendt's, Mack, Nernst, Plank, Somerville's, Stark, Wine, all the biggies. The reviews of his measurements, of his paper, included the following. From Edward Nicole's at Cornell University, the experimental difficulties of research of this character are indescribably great and the results obtained by Bracer to be accounted among the greatest achievements of modern physics. From William Maggie at Princeton, Brace brought observation to a degree of refinement not attained in the classical experiments of the great French and English investigators. And Heinrich Lorentz said Brace's observations were so sensitive that a difference between the principal refractive indices of even 10 to the minus 12th couldn't have escaped him. I think we may confidently conclude that it will be extremely difficult to reconcile the result of his observations and continued belief in an ether. One year later, Einstein published his seminal paper on the special theory of relativity on the electrodynamics of moving bodies and in it he makes reference to the unsuccessful attempts to discover any motion of the earth relative to the ether. And he acknowledged later on that there were experiments that proved that one does not even notice from anything on earth that it moves but that everything takes place on the earth as if the earth were in a state of rest. Now that confounding discovery, Einstein resolved with the principle of relativity. Speed of light is a constant for all observers regardless of the motion of the source of that light or the observer. He went on to recount that he puzzled about such things even when he was a student said you know when I had these thoughts in mind of the student if I had known about the strange results of Michelson's experiment I probably would have come to realize intuitively what a mistake it was to think of the earth as moving against an ether. You can understand why my personal struggle with the dilemma, you know, Michelson's experiment didn't play any role. Einstein continued to claim that he was unaware of that experiment when he contrived his theory. But Brace's work was analyzed in the same journal that Einstein was publishing in at the time and the commemorative Boltzmann edition was printed in Germany. He certainly had read both of them and Einstein and Lorentz where they came to be very close friends, confidants, they corresponded regularly. Brace by the way also corresponded with Lorentz. We have letters exchanged between him. It seems given Lorentz's admiration for Brace probably unlikely that the two never talked about the experiment. But nonetheless if Brace's experiment played no role in Einstein's development of special relativity it was absolutely essential to its acceptance worldwide. I'll just mention that in 1904, same time as Brace published that paper, construction began on the new physics building, something that he had been lobbying for almost since his arrival. It took two years to complete. But just as that building were entering the final stages of construction and the same month that his most recent paper of follow-up on the search for the ether was published, he took ill very suddenly and he died. Of sepsis that came from an infected tooth, something that seems outrageous today was something that people did pass away from and the building when it was completed was named in his honor. Now the idea that the speed of light is a constant for all observers regardless of the motion of the source of that light or the observer has consequences. And they're pretty astonishing and I'm sure you've heard at least of some of them. Time dilation, length contraction, the relative, relativistic increase of mass, the relativity of simultaneity, the prohibition against faster than light motion. And probably the very first one, this notion that time is relative is the most confounding. People struggle with that. I want to describe to you why it has to be true by even if you insist that light speed should be relative or that an ether really must exist. And I want you to join me on the bridge of the enterprise where everyone is at battle stations and they're about to execute an evasive action. In such situations we need flawless, rapid, efficient communication between all stations. And I'll highlight just a few important ones. Kirk awaits word from Starfleet command and it's communicated to him from bio hurrah at the speed of sound, right? And then he checks with engineering. Scotty responds and he communicates the action to the helm. But let's imagine a highly trained, well-practiced crew communicating even faster. So they respond reflexively on sight cues alone. A nod, a raised eyebrow, a blink, and those travel not at the speed of sound but at the speed of light. So as the enterprise, let's imagine, we're looking through the dome above the bridge into it as it races by the sky in impulse power at half the speed of light. When Kirk, when a hurrah sends the visual signal to the captain, when the light that left her station traveling at the speed of light reached where the captain's chair had been, the captain's chair, the whole bridge and the whole ship have moved forward half that distance. It's going to take twice as long as you would have expected in a stationary bridge for that signal to reach him. He has to check with Scotty, but of course by the time his signal reaches where Scotty's station had been, Scotty has moved. Well, it's going to take a little bit longer for him to accept the signal. Again, taking longer than it should have had everybody been at rest. Then Scotty returns the signal, but of course the captain's chair is a moving target, and so it takes longer than you would have anticipated. And the same is true when he communicates with the helm by the time his signal to the helm reaches where the helm was, the helm is slipped ahead. I don't care if you want to imagine that that communication is automated with driverless ships by computers, because the currents that flow through circuits are close to the speed of light. But every part of the computer chip has to respond correctly in sequence, and everything has to be clocked to do so. And if you follow the arguments that I just made, all those same sort of delays would happen in making that communication. And I would argue the same would be true in the transmission of signals through your synopses, your brain.  If light were carried by an ether and the speed of light were relative. And in fact, what would it do as you reached light speed on that ship? All those processes would never be able to take their next step. Things would stop. Same would be true for the condensation of water molecules into vapor, the buildup of collecting droplets. Because what that requires is that each water molecule sense the presence of the other water molecules. They're highly polar. They got to reorient themselves as they sense the presence of other charges around them for them to be able to draw on together and collect. That means even something as simple as the condensation of vapor into droplets or the crystallization into snowflakes in the air would be slowed on a fast moving world even if Einstein's relativity wasn't true and you wanted to think of the world order as being what they had assumed in the first place. As would all of our physiological life signs. Our hearts would pump slower. Our breathing would be reduced. We would think and perceive slower so in fact we would be unaware that our time was passing by more slowly. I thank you for your time and I'm happy to entertain any questions about brace or my relativity I guess. Thank you Dr. Kleis Sasan. I guess it is very illuminating presentation. I appreciated the history and seeing some of the old photographs and it's really amazing what was accomplished back in the day with the technology and the lack of the internet as you mentioned. I should invite everyone who has not already done so to come visit Jorgensen Hall because in the corridors of Jorgensen we have large showcases that display some of the instrumentations that were purchased by brace over a hundred years ago and some of the pieces that were constructed by brace so we've got an antique physics equipment museum in our building. Fantastic so we'll open it up for questions now and just as a reminder we want to bring the microphone to you so that we can get your name and question on the live stream or on Facebook so Becky has a microphone there's a question up here. My name is Tim Gay. I was under the impression that that first PhD you mentioned was in fact the first PhD given at the University of Nebraska. Correct. Which in fact was the first PhD given west of the Mississippi if I'm not mistaken. Also correct yeah yes even before any California system was graduating PhDs we were doing it here. So I'll ask a question while people might be thinking of a question. As you were looking through archives did you come across any information regarding how much time they spent on research versus teaching versus maybe service it was a small department. So you'll notice that I put a date for when brace came and started in 87 and then I talked specifically about a very fruitful period from 99 to 1900. So there is a considerable gap there. When brace came even though he was the physics professor he was teaching all classes of physics including at that time electrical engineering was physics. So he was teaching applied electricity he was teaching introduction to physics he was teaching a lot of mathematical courses relative to physics he had an incredibly heavy teaching load. So even though he was specialized it wasn't a lighter load than the generalists that were there teaching lots of subjects. Different than our model today. So it took him a while till he could convince the university to buy to hire enough faculty that he could find enough time to devote to research. So he had a slow period at start. Sorry Ronning here. Did brace construct his apparatus himself apart from the ones that he bought. Did he have workmen who constructed it for him. Did he train them or how did he have funds for it or is it his personal money that went into it. So he didn't have a lot of funds but he did have instrument makers. So when I showed that group shot there were two in that picture. One of them was actually a carpenter that's probably why they were using big beams and stuff right to set the equipment up and the workbench was what he had but he had to be a two instrument makers. He was always fighting to get them decent pay but they liked the work. So he purchased that polarimeter that I showed you right. That's on display at the showcases over at Jorgensen but he had to build a lot of the stuff himself. He had to build his own nickel prisms. He had to assemble the optics and stuff that you saw. That was stuff he had to build with the help of those two instrument makers. So Dan, I'm Margaret here. If I recall correctly Hudson Nicholson was the not only the chair of chemistry and physics but he was also the director of the egg experiment station and I do believe that he hired brief task which came with extra salary. Did you come across that? I didn't. I seem to recall he's the one who kept the measurements of temperature throughout the day. So for a while for the U.S. Meteorological Society there was a floor of the physics building where all of that equipment was but they actually had hired Sweeney to do that. So it wasn't Brace. If it was Brace it was a very short time. Yes. I'm actually a student. I find it interesting that at the turn of the 21st century the dominant cosmological model is the Lambda CDM invoking essentially merely phenomenological explanations for example dark energy, dark matter and yet these things aren't too different from the concept of the ether a century prior. How is the future of young scientists going to possibly return to this simpler view of the world if everybody is still teaching things which are simply placeholders for these phenomena? So it's interesting that the concept of ether never completely dies but in fact it's more than a century old. The ether dates back to the Greeks who argued that vacuums can't exist. So there always was some rational explanation for something like an ether although what the Greeks conceived its purpose for was different than what physicists argued when they imagined it was what carried waves of light and the new stuff that you talk about you know there's a Higgs field for example that permeates the universe. That's not the ether, it's a different thing, a different mechanism with a different purpose but it's very reminiscent of an ether because it does pervade the entire universe. So we will always have those ideas probably be recycled in new forms. I had sort of a random question. Oh sorry I'm frankly I'm a post doc. In one of the experiments that you described earlier done by Brace you mentioned that the current produced was 43 amps. I believe that was like the late 1800s. I'm wondering how he produced that much current. That's an immense amount of current. I'm sorry I don't know. Okay very no thank you. But he did I mentioned he did have two patents on electrical power generation and distribution and he he had some big powerful pieces in his lab. Any other questions? Okay let's thank Dr. Clayson again for the excellent presentation. We like to always give the Nebraska lecturers a thing to help them remember the lecture and the honor of giving it on behalf of the university. So Dan would like to present you with a framed poster of the lecture announcement and thank Dan again for a wonderful lecture on the history of Dr. Brace. Thank you.


Good morning, everyone. Our next speaker will be talking about TLS decryption attacks and backdoors to secure systems. Let's all welcome Mr. Chris Hinlen. Welcome to TLS decryption attacks and backdoors to secure systems. What we're going to be covering today is how weak authentication creates backdoors in modern security systems. We're going to be covering how state-sponsored attackers have already exploited those weaknesses. We're going to be talking about ways that you can copy their exploits and ways that you can build on their exploits and do more advanced attacks than what nation states have been caught doing. I suspect that some of them have already used these approaches, but they haven't been caught for quite a few of them. So a little bit about me and why you might want to listen to me. I've been configuring and protecting desktops and servers since 1998. I run a small business helping companies secure their infrastructure and their software development lifecycle. I have a few accepted phones starting with a file system phone in the Linux kernel a long time ago, followed by a couple of Google apps vulnerabilities, one of which got me into the Google Security Hall of Fame. I'm also on the organizing committee for B-Sides Vancouver Island and a totally shameless plug I'd like to encourage you all to try and buy the last eight tickets because there's only about eight tickets left and I'm hoping to see you there. You really need to get permission before doing these attacks or practicing any security testing. I don't want anyone here to go to jail and the laws vary from region to region. So make sure you have appropriate permission for your region and the regions of any machines that you're hoping to test or break into. So TLS was explicitly invented to prevent man in the middle attacks. It even says in early specs from about 1994 what a man in the middle attack is where there's three parties on the conversation, theoretically more, and that a bad guy sits between the client and the server on the network, intercepts the traffic, and effectively pretends to be the server. According to the specs, demand in the middle, oh, sorry, with SSL these attacks are impossible because of server certificates. The spec goes on to more reasons why they would be very difficult, but it depends on server certificates. And that is how attackers decrypt TLS encrypted traffic because many certificate authorities are willing to accept plain text authentication for domain ownership. So this means the plain text authentication makes certificate generation vulnerable to the exact attacks that certificates are supposed to prevent. Attackers then exploit the plain text communication and obtain certificates for domains they don't own and trick users into thinking they're the real server. So how do we know that attackers have decrypted TLS encrypted traffic? Well, the US government issued instructions to various government organizations on how to fix the problem. FireEye had some great details on all the ways the attacks happened and there's been many other, I believe this is a Cisco Talos that one, many other organizations commenting on it. It's hot outside and I'm thirsty. Oh, I think I went back one. So if you wanted to copy them, you could intercept the DNS traffic on the way from the CA to the DNS server for the domain you wanna attack. You could intercept HTTP traffic, SMTP traffic or different DNS traffic. And a lot of people might go, Chris, these all sound like the exact same thing. So I'm gonna leave the top part on there and I'm gonna explain why they're not. Let's say someone was trying to attack the city of Seattle's infrastructure. They have several options. They could attack the, or intercept traffic near the primary DNS server, which appears to be in New York, or near their mail server, which appears to be in Wyoming, or near the web server, which is in Seattle, or near the mail provider. So that would be Office 365's name servers. So these are totally different networks, totally different locations, where the same approximate type of attack can be launched. From the attacker's point of view, they might not just be targeting one domain. They might be trying to get as much data as they can. So if they break in upstream from the name server, there's thousands of domains they can get certificates for. If they break in upstream from Office 365, same thing, and so on and so forth for the other locations. So how would an attacker break into a router? We've seen several firmware vulnerabilities released. We've seen hard-coded passwords. There have been some compromised telecom companies and just this week we saw that AT&T staff had been accepting bribes to infect their own network. Now, sometimes there's alternatives. You don't wanna do those, cause you might get caught. So we've seen quite a few BGP attacks where traffic gets redirected to a different country than it was supposed to go through. You could, if you had say a search warrant, tap the least lines the traffic goes over. If you were wanting to attack a workplace that you had a connection on, you could use art poisoning within there and that approach works to get a certificate for that host's domain name. So people can use that to, a lot of companies will have like vpn.companyname.com or mail.companyname.com that points to the office network. If you were already inside the network, you could use that to get a certificate for their resolvable domain name and then start intercepting VPN traffic. Later on, I will be encouraging the audience if anyone wants to help with that and do a video on that, I will promote your work. You do have other options too. In the case of the successful attacks by the government of Iran or people who seem to be sponsored by them, they were breaking into name servers, domain registration servers, and mail servers are also an option. So most of the time, when I'm talking about breaking into a router, I'm not talking about your home or office router. I'm talking about moderately big routers all the way up to very big routers that may not fit in a single rack. So we're gonna start, this is a very basic attack. If the router was running Linux, you'd just be setting up network address translation.  No other traffic's being redirected right now and you can play around with that. If you wanted to, you could only redirect traffic from certain sources so that you were less likely to get caught because the people monitoring that traffic aren't on those IPs. We're setting up a super basic name server on the attack machine that provides new results to anyone querying them. Once we have those new results, we request a certificate from Let's Encrypt. I only have the examples with Let's Encrypt but I've successfully launched the exact same attack against Komodo and GoDaddy, both of whom set the standards for other CAs. CAs are certificate authorities. We test it and many browsers happily mark the site as secure. I chose Firefox because they even use a green lock whereas the other ones have phased out the green locks on secure sites. If we wanted to do it with HTTP, it's pretty much the same. It's just port 80 instead of 53 and for SMTP you're just switching the port again to 25. So we did configure a basic interception mail server. The main important thing is that we put a star in for host names so it intercept all email traffic. Now in this case we did a total fail. We hadn't gotten any certificates for the domain yet but that would only take a minute or two to cover your tracks. Unfortunately, very few organizations verify the certificate or require a certificate when sending confidential data. Kind of covered this one. So quick notes about the email interception. I didn't break into any mailboxes. I'm just sitting on the wire intercepting the mail. If you wanted to avoid detection, I'd highly recommend using a proxy server and relaying most of the traffic to the intended destination. I would probably skip anything mentioned in the words password reset or maybe even skip emails from the certificate authorities so the evidence of your attacks doesn't make it through to the destination mail server. So once we were intercepting email, what we noticed was that a lot of providers would send unencrypted usernames of their users. We were able to intercept the usernames and it went on and on and on. Now I saved all these results in a mailbox to make it easy for me to work with but we haven't broken into anyone's mailbox. This is just the results we got of all different organizations telling us usernames on their systems and in a moment we're gonna try and reset the passwords for those accounts. So this one's AWS, AWS didn't require TLS even though the user signed up with an encrypted connection. So they could have saved a record, this user mail server supports encrypted email but they chose not to. So here we are breaking it, intercepting a username, requesting a password reset link and breaking into a real estate company Cisco Miraki account using the same attacks we've talked about. This is a really big deal because once you break into their Cisco Miraki account you can add VPN connections into their office. You can add port forwarding, you can change the rules that segregate their network and stop certain machines from attacking other machines. It's a gold mine if you can intercept email near Cisco Miraki customers. Kept going and going and going. In the end we got into, we used the interception attacks to reset passwords on Cisco Miraki, firewalls, Google Nest, security cameras, AWS, Dropbox, OneDrive, Salesforce, LogMeIn, Carbonite, pretty much every system you can think of. In a lot of cases we're also able to bypass full disk encryption using these attacks because both Windows and Apple encourage users to set up their cloud account to be able to reset the password on their full disk encryption. So I sort of mentioned in the email portion you really wanna use a proxy to cover your tracks. That's a little beyond the scope of this presentation but if anyone wants to I'm happy to help you get a video going on the proxy style attacks. You can even use my attack server if you want to. So some of you might wanna protect a business from these attacks. I would strongly recommend getting certificates from a CA that doesn't support domain authentication. Some of the CA's that are focused on organizational validation only do org level certs and then you can at least test that the certificates are from that certificate authority. Monitor for certificates generated from your domain. Facebook has a feature for this. This is even recommended by the government. If someone generates a cert, you get an email letting you know.  If you see any fraudulent certs you gotta revoke them right away. You probably need to do a full investigation into how it was generated, how you're gonna prevent it. I'd love to see people in the room fighting for stronger domain authentication standards and you'll probably need to automate testing of your DNS records so you know when they're being manipulated. So how could certificate authorities stop these attacks? They could use the same technologies that they're encouraging for HTTPS on all steps of the validation process. DNS, SMTP, just have mandatory TLS when validating domain ownerships. They could, I would suggest checking all name servers when authenticating a domain. That way if one of them was compromised they would have to compromise all the name servers to use that compromise. To make sure that the name servers that are validating these requests aren't using fake certs that were generated today, yesterday or up until the problem is fixed I'd require organizational validation on the name servers. And in the event that the certificate is no longer has its authentication values sitting on the name server I would set the CAs up to automatically revoke those certs. The only CA that I know of who's doing that right now is Amazon. If you have a cert in place with Amazon they recheck your DNS values to make sure that you still have the value proving your domain ownership and they give you a warning if it disappears I know because I deleted one of those values and then you have a chance to put it back. So I'd love to see the browsers putting pressure on CAs to protect their users and even domain owners. If the site doesn't support encrypted DNS I'd start with a mild not secure message. Not the big red message but just put a little pressure on people because we know that those messages in Chrome get action from customers. Similarly, if they don't support encrypted email warn the user this isn't a site that takes security seriously and it's a lot of government sites that don't support encrypted email because some of the firewalls they use for spam filtering it's block encrypted email by default or block transport layer security on the email. So I think the users visiting those sites should know that the site isn't taking security seriously and it not to trust the site. NECAs that are continue to use plain text authentication to prove domain ownership I would refuse to trust them and then as new standards become more common I would warn users about sites using old certificates that don't meet the modern standards. And that last one of warning I haven't seen it at the browser level but the payment card industry requires that you have a properly generated cert in terms of the random numbers that were used. So I'm hoping that the payment card industry and the web browsers could expand towards warning people about other weak authentication. The main message of today is that weak authentication provides a backdoor to many secure and encrypted systems. If anyone here wants to build on the work I'd love to help you make videos using Cisco or Juniper routers as part of the simulation. I'd love to see an ARP cache poisoning video videos of proxies and other open source tools being used to reduce the risk of being caught. There's quite a few people I need to thank. My friend Adam Bennett helped with a lot of the account creation. John Seymour was my mentor at the Beesides Las Vegas Proving Ground last year and he helped me get some of this ready. Jerry Desim of Micro Focus. He had some related CVs he accepted my LinkedIn in mail and helped me find a lot of resources that helped. Chris Kubeca, she provided some awesome research about a year ago on email interception attacks and the Okanagan Information and Security Group let me practice when I was nowhere near ready and that was very helpful to getting ready. If any of you want to connect with me I'm on Twitter at Chris Hanlon CA. You got an email that will work for a while to reach me. If I get too much spam there I'll probably drop it but works for now and I'd give you my real email if you email me on there. In terms of following me on Twitter if your profile says Infosec or Noob I will follow back. You may wonder why I follow Noobs but I think that they're the future of the industry so anyone who admits that they're a Noob I will follow them. Does anyone have any questions? Yes? We've got a mic for questions. So if you have questions come and line up up here by me and I'll be happy to hand you a mic so everybody can hear you. Is there anything you can do from like the service provider standpoint when if you're concerned that say your password reset emails are getting intercepted in this way or like, you know. Yes. Two-factor authentication is probably your best bet and it needs to be real two-factor because I've found some where they have a downgrade to email and if there's an option to reset the password via email along with an option to get the two-factor token via email that's not two factors. That's one factor twice. So you mentioned one of your suggestions for mitigation was we'll do TLS on everything, right? With TNS and TLS when we're doing the domain validation. So is the suggestion there that just like, so we have to bootstrap our trust from somewhere when we've got a new server so you're saying we'll use some trusted thing where we, because you need it, if you want to do mutual TLS you need to start on both sides already so are you saying we'll just bootstrap our trust from somewhere else where we already have an existing trust? I guess the big thing is, I also asked that the name servers have to have an organizational validation so that typically involves proof that you run the organization which is done offline and there's a relatively limited number of name servers compared to the total number of domains so our trust I guess would be in notaries, lawyers and similar people to prove ownership of name servers. Sounds good, thanks. You mentioned on some of the redirects attacks, I could see how you're doing that if you're already inside the network but functionally or like practically how could that be done from the internet or like on the other side of the world? There's been quite a few firmware vulnerabilities and major routers. There's also the element of insiders at the telecom companies either being bribed or just realizing the potential for money and we have seen the BGP attacks where like millions of dollars of cryptocurrency was stolen from one of them so that and even in the last few months we've seen standard network traffic being redirected through China that was intended to go between the EU and the US so it does happen. Would you agree that if on the firmware argument if you just kept up to date with patches that would lessen your vulnerability? It definitely lessens the vulnerability of the ISP but users don't know how good their customers including government customers don't get a great idea of how well their network presence provider is monitoring for intrusions or keeping their stuff up to date and I think that's really you don't know how well your ISP is doing but it only takes a one time mistake for a huge amount of damage and the whole point of encrypted connections was that we didn't need to trust the certificate authorities. Thank you sir. Or sorry, we didn't need to trust the internet providers. A few years back we used to have extended domain evaluation certificates where the browser is to display like a green bar and it disappeared and so from a consumer point of view doesn't understand cryptography that's using the browser to go to a bank or something like that. There's no difference between some certificates that's gone through extended validation to make sure they're the owner of the certificate but somebody who went to let's encrypt and maybe got a free certificate, right? So why there's no distinction between now I should be able to know as a consumer whether you know how trustworthy it is like a green bar for example. The big reason why those got pulled out is that criminals were getting certificates that met the green bar standard and users who didn't really understand the system put a lot of trust in the green bar. So I think we're moving in a direction of warning when things don't meet good standards with warnings about insecurity rather than trying to guess how secure someone is. If I am a city bank for example, right, I have to really prove that I am really a representative bank that's how to say criminal kind of have the credentials to actually prove like a physical online message to make sure that you are the owner of the domain or something like that. I suppose just an email saying that I own it. Yeah, so that's why we need higher standards on the verification of domain ownership. Would DNS sec provide any form of mitigation or would that just be another attack vector to abuse in this case? DNS sec would likely help but because TLS is on so many protocols I think that DNS over TLS is more likely to gain market share. Thank you very much indeed. Just a quick comment on your previous answer about extended validation certificates. It wasn't so much that users were putting a lot of trust in them and therefore if a, as you mentioned, criminal was able to get hold of one incorrectly it was too powerful. Research was showing that nobody noticed them. Even those people with training and there are some instances for example, a large financial institution through a misconfiguration was failing to serve EV certificates for quite a while and nobody noticed. So they were only adding to confusion with no benefit that number of studies could measure. But you are the point to perfectly correct. Thank you. So what is your recommendation for the next step? You discover that your domain has a rogue certificate issued when certain certificate authorities such as let's encrypt have an explicit policy against revoking certificates that have been determined to be rogue. I was not aware about the failure to revoke let's encrypt. Those ones are only good for three months but you're going to need to investigate how they got that certificate. To some extent you're also going to need to prevent the traffic from getting there but I didn't know that let's encrypt wouldn't revoke. Thank you. Any further questions? Do you share the presentation slides? I will. Okay. I'll tag the crypto privacy village with a link to the slides. Or actually do people, oh. I might have a way to show them right away so you can take pictures. No, well I guess that is a public link. It's pretty long to type. But I was planning on using a little clicker thing and there's radio frequency attacks against them so I went into a lockdown account and this is the public link to the presentation slides but I'll tag the crypto privacy village with a short one very shortly. Any final questions? All right, one more big and random applause for Chris. Thank you.