I think that's probably the best way because you otherwise would have to sign out and sign back in. So if you could just in the chat box in some place indicate your name, your full name and your CCA, we'll make sure that you get recorded. Well in our presentation today, we want to cover three main topics. The first will be evaluation of plant stands followed by weed identification control by Kirk Howard. He's in the Department of Plant Sciences, NDSU, and the final speaker will be Lake Vanderbors with Ducks Unlimited. We'll talk about disease and nitrogen management. I think after Kirk's presentation, we'll certainly take time for him to answer some questions. He'll have to leave. If I finish in good time, I might take a few questions on my section, but please feel free to hold questions to the end as well. We will take whatever time needs we do plan to finish in general terms after an hour. So I'm Joel Ransom, Extension Agronomist for Serocrops. My part of my presentation, I'm going to talk about evaluating plant stands. And as you all know, having a good stand in this spring is key to a productive winter weed crop. And I've got a glow graph there that shows the relationship of percent winter survival in yield. And so ultimately, we want to have a reasonable plant stand. The question is, how much do we really need? And what are some of the factors that are going to affect survival? And I think this is one of the reasons we want to talk about this today is because we did make, we did start our winter weed crop last fall in pretty poor conditions. But the factors that are going to impact the amount of winter survival are going to be the environment. We have little or no control over that. Temperature at the crown is probably the most definitive of the environmental factors that we're going to talk about. The second would be the state of hardening, which is a time of year. We'll talk a little more detail about that. The variety's fallen and the size and bigger the plant in the fall. So these would be the four main factors that we're going to be influencing the amount of winter survival that we have. And if we look at the general graph that was indicating what temperatures our plants can tolerate cold, you can see this top graph is some data from Kansas State. You see that we start as the plant is emerging. It is not able to tolerate cold. It's kind of like spring wind in that state. And as we go through a period of cold, it will harden off. And it gets to the point where it will be able to withstand cold temperature down to about 10 degrees Fahrenheit, minus 10 degrees Fahrenheit. And it will persist in that level of winter hardiness until about February. And at that point, the reserves start to diminish and it becomes more susceptible to cold. And we see that as we move into the mush where we are now, the ability to withstand cold is significantly reduced. And it's not uncommon to have plant stands that had made it to the winter up to this point actually be lost when you go through a cycle of freezing and thawing. And you can see that there's a pretty wide band of temperatures that can be tolerated. It really depends on the plants, the reserves in the plant, the variety of its own, and the kinds of fluctuations in the temperature. So it's pretty hard to predict precisely what kind of, you know, what the plant is going to be able to withstand. Let me just review with some data from last year. This was a winter survival model that was put up in Canada. Just one thing to do. OK. So if you want. That's OK. If you want. And that arrow will move around. All right. So last year, sorry about that little intervention. It was a hopefully a useful one. I was having all kinds of fun with my pointer and you weren't seeing it. But last year we did have a winter wheat survival model. It was very descriptive in kind of showing how the winter wheat plant tolerates cold. And depending on the variety, you can see that I talk and and sephodora were able to tolerate just about minus four Fahrenheit. And as you get further into the spring. You can see that there were cases where we actually had winter kill as a result of plant being less hearty and temperature being too cold. We look briefly at where we're at. This is some data that John was he's been recording and the top the top graph shows the winter golden valley. And if we look at the. The. The soil temperatures under a short stubble. We can see that certainly the temperatures are less captured as much snow. But in general, I would say that those temperatures, none of them are below what we say is a critical level for winter winter kill. We go to Cass County, the bottom graph, we can see that we have had some temperatures, soil temperatures. I think these are about one inch depth where our crown likely be down. But again, probably because of the snow cover with that, that our temperatures, at least in these areas, haven't been excessively low. And also we have to be too concerned about winter. I talked about variety being important and this is these are some data I collected in 2003 and four that I haven't been able to replicate. It was a perfect year for having some oil and looking at the soybean residue. You can see that our varieties coming from more southern locations. We had a very high level of mortality. Whereas with a little bit of snow cover under the seats, wheat residue, all of our varieties were able to tolerate the winter. So variety choice is really critical and I know we introduced a lot of southern kind of winter wheat varieties into our system and so this might be a year where we see some of those failing because of the late planting and other factors. We're in the last couple of years, we've had really good survival because of the snow cover and other things. I mentioned the size of the plant going into the fall can have an impact on the winter hardiness and here's just an example of very late planted, small plants, very few reserves. It's going to have less ability to tolerate the long cold and this plant up here. And you can't actually plant too early and have too big a plant. So we don't have that problem in North Dakota very often because by the time you get in and plant that recommended date, you don't get a plant that's much bigger than kind of what that person looks like. So I think this is one of the issues we're a little concerned about. We had very late emergence because we planted late. The range didn't come until much later than normal and so we probably had a lot of plants that just kind of set there and very early got to start. So let's talk about what constitutes a reasonable stand. You want to go out and count several areas. Probably, I've mentioned two foot length. Probably five foot would be more realistic and you want to do it in representative areas of the field. You may have some parts of the field where you have big gaps and you won't count those differently than say other more normal fields. You want to evaluate for bigger and we have a kind of a general recommendation that we can tolerate plant stands down to as low as five plants per foot. That's probably on our lower end for winter wheat. If you compare that to spring, you can see that we can tolerate about half the stand that we can with winter wheat or with spring wheat. Here's just some data showing you that bottom graph would be coming from Mandan that you really start to see a yield reduction when the plant stand is below seven or eight. But you probably are able to maintain yield sufficient to make it profitable to keep that stand if even more than five plants per square foot. This is some data that I showed you previously showing you the relationship between yield and plant stand. And here we had the down as low as 20% survival. This would have been kind of a objective evaluation that we were getting up to 60 bushels which would indicate that you probably want to hang on to that. Some other data, this is put together by Steve Dvorak looking at some of the range of varieties over a number of years. And you can see that again probably about that 30 to 40% stand in the spring is going to be a critical level where you want to keep it versus where you want to think about telling it up in plan. I'm going to skip the slide in that slide but basically just showing you the same relationships as you get into that 55 and above is not so problematic. This might be what your field will look like in the spring if you're evaluating plant stand. And you can see that in this case the leaves have all burned off and some years we keep green leaves throughout the winter. But just because hot leaves have been frosted off doesn't mean the plant is dead. I have a really nice technique for determining quickly whether your plants are dead out there. You can dig them up, nice to wash the dirt off, clip back the leaf tips, put them in a bag, keep it warm and usually within 24 hours you can see something emerging. If you don't need it by two days then you can be a little bit worried. You can see in this case a nice little green shoot starting to emerge after probably after. So in summary I think our optimum for winter wheat would be to have a stand in that 20 to 25 plants per square foot. But stands between 12 and 15 square foot are more than adequate. And stands as low as even five per square foot have yielded well if conditions are conducive to children development. And you want to consider how uniform the stand is across the fields. Certainly you can have big patches and it's not uncommon to have big patches where you lose stands and other parts would be normal. And you may have to develop a strategy for how to fill in those patches. It's not a good idea to leave patches just the weeds. Others have plants in spring weight but you can imagine the challenges have also hardly seen two classes of wheat at the same time. So you kind of have to have a strategy in place as to how you might handle those patches. And I think that bag test is really useful for those who are a little worried about whether they're crop mated or not. And it's as simple as going and getting a few plants, taking the dirt off, soil off the plants, cutting back the tissue and observing injury. This fall as I mentioned previously we planted late. The plants got emerging late. And so these small ceilings are very difficult to evaluate. And I think it's going to take a while before they'll start to emerge and show any green. And I think the message here would be we'll probably have to be patient and see how things be going once we have snowmills and temperatures. We'll want to discover a crop that in a week later will show some real green and bigger. And I think their question that might have coming our way is that we don't have enough material. And I think that most folks that I've talked to would say it's very unusual that we didn't get enough inhibition and started the germination process in the fall. And maybe even the spring if that's the case. We won't have enough accumulated cold weather to do vernalization. So I don't think that's going to be an adequate standard. So with that, I think I'll probably have time for one question. If somebody wants to ask a question then I'll turn it over for the topic on weed control and identification. I can't see any hands up there. I think Kurt, I'll turn it over. Thanks, Joel. Joel and Blake had asked me to come in and talk a little bit about the weed control, especially the winter annual weed complex. And I had the opportunity to stick a few other things in there as well, especially towards the end. Some of you may have been involved with the culture monitoring and the sample collections that we did over the winter. And I've got some information there as well as the response of the plant samples to chloroxapir. So I think thinking about winter weeds and definitely the winter annual grass complex causes consternations for all kinds of people. Treat sheets being a species that we don't see in North Dakota very often. There's definitely more of them on tan weed. But areas where there's an issue that definitely occurs in enough populations where it definitely reduces yield. And as you can see the heads there describe those as an open football shape as opposed to Japanese brome which we'll be looking at a little bit. Relatively little pubescence on leaf tissue membrane as short membrane as ligule. And Japanese brome does have a very short ligule. It has a very dense map of hairs along the sheets of the leaf as well as hairs on the leaf surface of the leaf on the blade. Still fairly small so it's not easy. It's not like Yellow Foxdale where you see those very long, scraggly hairs at the base of the leaf blade but it creates a shroud around the plants so you can see plants kind of have a halo to them. And as you see this in this next slide that dense map very heavily pubescent and the amount of pubescent is related to the temperature regime that it's been exposed to as well as some of the environmental conditions related to moisture. So they have dense and pubescent we can have fairly sparse pubescent but they tend to be quite long relative to the relative to the downy brome surface. And then with the seed head there you can see it's more of a compact football shape. The florets as individual seeds do not open up nearly as much as trick sheets. The downy brome is really the one that causes us all of our problems in North Dakota. It is more difficult to control herbicides and is able to germinate and emerge in the spring as along with Japanese brome and easily produced seed. I talked briefly previously about fertilization of wicked wheat crop that needs to happen with these plants as well and even the cooler spring temperatures in the evenings is enough to initiate seed production for these plants. So just because it emerges late in the spring doesn't necessarily you're going to avoid seed production. This also has dense sheath pairs but they're quite a bit shorter and I think the entire field of the plant has a lot more of a velvety touch. The downy brome tends to be a little bit more prone to purple coloration that's brought on by the cold through the winter. You can see the downy brome in wheat the tint of purple coloration, reddish coloration and then also one of the seeds with long on that will give the downy brome inflorescence a much more feathery appearance as you see on the right as opposed to the tight clusters of the football shape on this of the Japanese brome seed flores. The downy brome like I said before is definitely more difficult to control than Japanese brome and when it establishes in the fall to wait until the spring it can create very difficult control situations. This control tends to be more fall the plants are smaller they haven't initiated as many tillers and there's just not as much tissue to try to get control with the herbicide. Control options before the winter wheat is in the ground of course include glyphosate which provides a very exceptional control and we do have two products or prepare that are registered before wheat and both of those can provide some suppression. I would not necessarily expect complete full season control but they will help reduce the herbicide competition so that you have smaller plants later on post-emergeous treatment. As far as post-emergeance if you have clear field wheat beyond is definitely a good option and I've also found the most complex to be very good options for control of these winter annual crops. Maverick can provide a very good level of control however in working for the high soil age we definitely have issues with carryover as there's probably not a lot of Maverick used except for areas where you know that you're going to be coming back to cereals in the fall of the season. And then Sierra Foreverist for Empire Max do provide good suppression and if the plants are small enough we will provide adequate control of the downy grown and those that are strong enough they should provide excellent control of the Japanese grown. Crochtail Barley is another plant that's becoming an issue throughout the state and in the seedling stage it is very small, very thin leaves also has pubescent along the leaf sheath but the leaf blades are nearer and at the seedling stage is where you really need to control this because as a perennial it truly establishes it is difficult to control with anything and when we get to that stage for the post-emergence treatments Olympus has provided the best activity can kill some of the plants but more there we're just trying to prevent production for the following season other products tend to be a little bit weaker on it PowerFlex I haven't had enough experience to know whether it controls well or not Brickley Lettuce would be one of the broadleaf winter annuals still looks like dandelion if you turn the leaf over you have the long rows of spiny rows off the mid-grip and Brickley Lettuce is a composite species it is controlled very effectively by many of the growth regulators but especially perillipotent products such as curtail curtailam horseweed I see my D fell down below as it moved from one system to the other but horseweed is becoming a large duration in North Dakota because of the resistance that has developed to glyphosate we have confirmed that in Cass County there are other areas of LeMore and Pierce and McIntosh for samples that come in where we suspect there could be some resistance but haven't been tested yet without use of glyphosate really by controlling young resets plant growth regulators and ALS inhibitors at those early growth stages tend to be very effective Field penny press we can get into the mustard side of things recognized by the penny-shaped seed pods that can close the seeds it takes off very early in the spring and ALS inhibitors are very effective even once this plant starts to fold a couple of other and mustard family at Tans and mustard inflicts meat in very finely divided leaves and they're also controlled at the early growth stages of control so that it does not extend to the stage followers are being produced you may still be able to get control with ALS inhibitors especially with combination of a phenoxytype herbicide but control definitely starts to get more limited comparing this with a perennial this is false chamomile false chamomile once it is established as a perennial again control combinations of ALS products plus a phenoxy have done quite well but a lot of the herbicides used in cereals that are based on contact type products will not be very effective on this week false chamomile once it starts to flower it gets that typical daisy flower head on it the other thing that I wanted to talk about for a little bit was the kosher monitoring we have several fields that people sent in samples last year this was initiated because we had two specific sites one up in Pierce County and one corner of Stuttsman County that glyphosate resistance was suspected in 2011 during greenhouse testing we did that both of these locations had a very elevated level of resistance where even a gallon more than a gallon of power max was not controlling all of the plants and compared with that with 11 ounces that would control every plant in the susceptible check definitely indicated that we had a problem the same seed lot was exposed and we've treated with clarity and starian ultra trying to identify some of the other control options that might be available for cereals we were not pleased with the response indicating here definite survival and very big growth after full labeled rates of clarity even in corn or the start of the rate a high use rate 5.7 fluid ounces does not kill all of the plants we had several samples come in from around the state mostly from the eastern half as you can see on the map here we did have a few kosher samples coming in from the far western the I-95 corridor and these were seeded into pots in the green house we had a susceptible check in the upper right hand quarter and a resistant check in the lower left hand quarter spraying these pots with glyphosates typical response and more than 50% of the populations were controlled easily with that standard rate of power max the green in the corner there of course with the resistant check from Pierce County but we did have several of the flaps that had different amounts of regrow depending on if it was a 1x or essentially a 3x rate in some of those pots the control was almost nonexistent we also sprayed all of the foroxapyr and typical response to foroxapyr would not be complete plant death these plants that are very injured however can start to recover after a couple of weeks and start to produce growth this is a serious concern for our late season weed management because those plants that remain down they can't be all season long once you remove the weed canopy they can start to produce new shoots and produce several thousand seeds per plant or harvest so on the kosher side of things what are some of the other options we do have very effective use of glyphosate or foroxapyr still in much of the state however we do have foroxapyr working as well as it should from essentially every area where we've received samples in those areas cereals of course will rely on buck drill with either permoxanil copac product seems to be working quite well yet in other crops where you can use atrazine that has been very effective DPO inhibitors the aim is very effective in crop if the plants again are less than two inches tall a sharpen can be an effective pre-plant burn down at moderate use rates however we cannot expect very much soil residual from a sharpen for managing the kosher into the season essentially it comes down to making sure that you don't have plants there when your crop is established and trying to manage those emerging plants before they get beyond about three inches in height with the sweet products that we have available I know there's a lot of areas that are listening probably no till or minimum till but steel is still probably most effective and reliable ocean management tool because of the short soil residual of the seed and the susceptibility of the plants to cultivation I believe that might be the nice slide set so if you have any questions you might be able to answer some on issues or other topics that might be pressing in your mind there's a couple of them there that I recognize good morning everybody it doesn't look like we have many questions coming in I will be able to stick around for a little while so maybe if you type in questions for me as Blake is doing some of his discussion before I have to leave I can still maybe answer those Thanks Joel and Kurt I want to thank NDSU and particularly Scott for helping coordinate the webinar and for all the support we've had in the promotion of it I went back up to one didn't I Yeah I want to redo this You can start over Okay here we go You can click on the name Let's get started here and try to move rather quickly if I can and what we're going to talk about a little bit this morning is a little bit on nitrogen management and then some on disease management that we've been doing with NDSU and SDSU and ourselves if we just look at that first slide you're taking a look at there the soil test plus the applied in and this is over trials BU conducted in North Central Northeast South Dakota and then through the central range of North Dakota all the way from Crosby to Jamestown to Allendale kind of on that kind of a line and probably about 80 to 100 miles to the side of it and what you'll see there in the next few levels we're probably coming someplace between 180 and 220 pounds of total available land if you look at at John Lukach's data from north east North Dakota you'll see that from 2009 to 2011 since John started working on winter week you'll see probably pretty close to that same amount of nitrogen maybe slightly higher on the top end the one thing that was kind of interesting and when we added 2012 data into the BU sites we added another five locations and you'll note that that bottom line has shifted a little bit to the left a little bit less nitrogen and the reason for that we believe is if you remember the winter was open we were warm most of the winter and then March was about 15 degrees and we think there was probably quite a bit of extra conversion going on in the soils from the organic matter and so we had actually two sites that responded to an additional end we had two sites that showed no response to additional end once we got to that per 60 bushels yield goal plane and then we had one site where actually every level of end that we added decreased yield further and that was due to the fact that the additional end caused lodging so the more end we put on the more lodging we had and the lower the yields became with that nitrogen base through farm experience and pass yield experiences but actually now in the 13 years we've been doing these trials this is the first year we've been able to document it in the trial setting so that does happen so if we look at the amount of nitrogen talking with Ron Gelderman South Dakota State STSU is still at two and a half pounds NDSU is still at two and a half pounds per bushel of actual nitrogen some data that we've been using in our DU studies from ARS that was conducted for a long period of time in winter wheat at Mandan North Dakota and at Sydney Montana was 2.25 pounds and per bushel for 12% protein we're pretty comfortable with that we think at some point in time hopefully with more data we'll actually be able to reduce that number further and I think as some of these new breeding programs and techniques come online now some groups focus on greater efficiency of the nitrogen as well in these new varieties one thing I just wanted to point out I showed this slide last year is that we just need to remember working with our producers or if you are a producer is that winter wheat has a higher yield potential than the spring seeded wheat by 20 to 30% so you need to take that into account when you design your nitrogen programs for the spring or if you've already done it last fall the other thing to remember in that is I think winter wheat probably can get by with that quarter pound less per bushel than the spring grains can so you do gain some efficiencies there but probably not enough to make up the fact that you need to add more into your winter wheat to attain those yields one thing is we talked about the maximum in needed for maximum yield to be in that 180 to 220 to 230 range obviously economics play an impact on that and what that final rate will actually be and you can see on this slide I'm going to see if I can make this point at work but over on the left side you've got four and six dollar wheat so you've got two sets of lines obviously you've got higher placed wheat you can afford to put more nitrogen on on the crop the other thing that you've got is if you look on the par right you've got 50 cent and which is the blue lines and the 75 cent which is the green lines so the cost of ant is going to impact where that line is at the other issue that you have is the end protein discounts or no protein discounts obviously if you're looking at things where there's no discount on the protein on the top with the blue on the top we reach our maximum end level at an earlier stage but if you have discounts you'll notice then you actually need more nitrogen to reach your top net profit potential for the winter wheat so you can take a look at this slide more as we will post on our websites at NDSU and BU and study these a little bit but they're kind of interesting and some day I hope we can develop a table that will allow us to plug in the discounts, plug in the cost of the nitrogen and the price of the wheat and be able to predict more closely the amount of end that we should probably look at on the given year. If we look at placement Steve pulled together some data for me from our last two years of end trials that incorporate timing as well and you'll note that there's really no difference in yield from the seeding time application will replace the end of the soil surface to the surface applications of the 28 percent with stream bars and so if you look at it which would be breaking dormancy and then we've got the combination of seeding which is the urea down below the surface at seeding time along with the early stream bar and then the last one is the seeding with the late stream bar. You can see there's less than a bushel difference in those over the two year period and this follows a very similar pattern to the numbers that we generated from 04 to 207 in North and South Dakota in that dropout so this pattern of the last two years and our end trials follows that same time span in North and South Dakota when we did 04 to 08 but that fall seeding application actually does have a tendency to have a little less protein than the spring application and it generally runs anywhere from three tenths all the way up to six tenths less than the spring applications and I think that the graph basically tells you too what you put on the later you put it on the higher the protein levels will be just one site this year where we did see response through the full rate of nitrogen rates was that Crosby North Dakota and we had fall application versus spring application and then nitrogen rates as well but if you look at treatments N2 3 and 4 on the left those were urea out seeding time placed in a deep bend and then N5, 6 and 7 were stream bars and goal rate 3 was 85 and 4 was 110 and 5, 6 and 7 were corresponding to one thing you'll note was that there was probably slightly higher yield to the fall application with the urea when you average those three at 91.5 versus the stream bar in at 89.5 statistically obviously not different but we were noticing that pretty consistently this year and we think that was probably due to the fact that we had the urea place below ground we did not have we did have excess moisture obviously following seeding and during the course of this growing season and where we looked at the UAN sometimes the rainfall didn't come following the UAN application from anywhere from 2 to 4 weeks following the UAN application so there was some delay in the availability of the UAN and if you look at the proteins on the right hand side the fertilizer rates within the N234 and then within the N567 you'll see increasing levels of protein which you would expect the other thing again just showing the protein on the right to the average of 11.6% for the urea in the fall versus the 12.2% for the UAN in the spring just pointing out the fact that some spring nitrogen has the ability to increase your protein levels for you then looking at our watery stage application in other words applying 10 gallons of 28% with 10 gallons of water for a total of 20 gallons per acre with a flat-found nozzle trying to increase your proteins right after flower but before the kernel leaves that watery stage and hasn't reached the milk stage but if you look at the yields of the let me get the pointer here comparing the watery stage versus the no watery stage and you can see that the yields were identical in some cases depending on how the applications go some people do worry about the water stage application reducing yields due to leaf burn we did not have any issue with that the last two years if you look at the probe levels on the right side you'll note that for the 60 bushel yield goal when you increase those nitrogen levels for the 85 bushel we increased the amount of protein from 12.1 to 13.1 and you can see that similar trend under the no watery stage nitrogen applications or excuse me with no actual application at the watery stage you can see that the increased levels of animals increase the protein but I think the important thing here is if you look at the yellow shaded area in the bottom the watery stage application gives 12.8% rotation versus none at 11.7 for the average so we picked almost a full point of protein up this year from that application last year those numbers were about half percent we look at some information that Ron Gelderman shared with us in December and I want to thank Ron for these Ron had done some trials with ESN on urea and its influence on winter wheat yield the thing that I want to point out is you'll notice these are two locations for pier and wall and you can see there are some tremendous yields at pier 102 with the fall application of urea and 107 with the spring application of urea the thing that you'll notice though is he added ESN they were both 102 and with that spring application he lost about 5 bushels and you'll see that he lost 8 bushels with the spring application at wall and my guess is this was 100% ESN treated urea ESN met urea to a point where it didn't benefit yield and then you'll notice in the next slide that you'll see that the protein levels actually increased a little bit and that would probably fit that reasoning and ESN held that nitrogen so if you're going to use ESN with your winter wheat application just remember winter wheat needs that nitrogen early you're probably definitely not going to want to put 100% urea spread out there in the spring of the year on your winter wheat we look at this next slide looking at agritain this is some work that John Lukacz has done up in northeast North Dakota he actually had six sites in 2010 and 2011 and I dropped the one site I was a little uncomfortable with the urea agritain had dropped its yield pretty substantially I think it's one of those outlier type situations but at any rate you can take a look at the yields at the various locations for 10 and 11 and you'll note in several cases there's no difference in yield but in two or three cases there are some differences in yield and if you look at the averages on the far right you can see the urea was basically 80 bushels the urea plus agritain was 83.8 or about 84 and then the ammonium nitrate just not to have any volatility because it's 100% nitrate at 83.3 so it's kind of a check to the agritain so John says it's not meant to work every year because you hope you're going to get rain with that urea on the surface and it's going to take it in and I agree with John so it's in those circumstances where maybe like in 2012 we applied the urea early we had an early spring we didn't get any rainfall for two to four weeks so you hope to expect to see a response and on some of the trials that we did in 2012 we did not see a response to the agritain and again I think it went back to the fact that we were getting that urea it wasn't an issue I think this is probably the most important thing I'm going to show in my portion of the slides today Joel talked about stands and stage of winter wheat and if you look at the top left-hand picture you'll notice that the development here is from below the sole surface all the way up to one leaf stage and this was actually in the fall of 2011 at our mine out location at wind field and then if you look at the bottom slide on the right this was actually a little fallow strip plot area that hadn't been seeded the prior year we seeded right through those areas you can see we had two and a half wheat there versus the stage that we had one of the things that we tell growers is our goal is to have approximately 50 to 70 inches per square foot when we come to that harvest stage now obviously if we're seeding and we're seeding at rates of 25 to 35 plants per square foot we're going to need to make up some time here so we're going to need to want to encourage some tillage and so we're going to want to probably put some nitrogen on early to enhance that the tillage prospect so if you look at the two pictures in the two corners we've got good bigger on the field on the left but we've got very poor bigger on the field on the right and what you want to do is just as soon as you can traffic that field once the frost is out it's probably to get 15 to 25 pounds of ant on in some form Urea or 28% or whatever form you can get it on and hopefully get some rain and help stimulate the tillage. Just looking I'm going to cover now just a little bit on disease management and mainly it's on fungicide timing applications and on response in 2012 we saw the least response we've seen in the past three to four or possibly five years to fungicide applications as you recall it was dry early so can spot wasn't a big issue and scab was not a big issue we did have some stripe rust in some locations in the eastern Dakota but you can see that in our 2012 variety trials at your scatter across north and south Dakota we had a 3.8 bushel response across all varieties and that obviously varied from location to location and from variety to variety but with about 5% return increase in yield I should say. We looked at 2009 it was a 10.2 bushel response with about 15% increase in yield 2010 was a 14.2 bushel with about a 20% response and 2011 was a 12.9 or 13 bushel with about a 24% increase and so we look at that average across all those years with 12 included it's been about a 10 bushel response with about a 15% increase in yield. John gave some data I'm not going to go through this slide but I just wanted to show it to you and you can go back to again to the websites and dig into this if you want but this is John's data from northeast North Dakota from 9, 10, 11 and 12 and from that data these next three or four slides are summarized from that data but if you look at at the sites there was 22 experiments that contain the Passaro application at Erlich-Lauer in the studio with the herbicide and then the Passaro at the Erlich-Lauer and then the check and you can see that in in those years in northeast North Dakota he's getting most of this benefit from the Passaro application at the Erlich-Lauer so in three out of 22 experiments as indicated below he had a five bushel of greater yield increase with the herbicide timing with the fungicide so if you look at the next one you broke that further apart and it's indicating that in five out of 14 experiments there was a five bushel of greater yield increase due to the flag of the fungicide and then in 12 out of 14 experiments it was due to the Erlich-Lauer fungicide so for John in that area that is pretty strong evidence that application at that Erlich-Lauer stage is really important and he went on to further break out a few other comparisons and indicating that in four out of ten experiments Passaro treatments yielded five bushel are more than five bushel of greater yield and in the case of Passaro it was eight out of ten experiments in that particular series I think many of you probably remember Marx-McMullin the end issue pathologist that retired last year always indicating that she felt that the Passaro for the difference in cost between that and the full cares and the generics and John's data here is just indicating the same if you look at the next statement of the series I think if you look further south say south of highway two and west of highway there you'll see those early herbicide treatments or the combination of herbicide and fungicide pay more than they do in John's area because hand spot is a bigger issue as you move into a different climate compared to what John has up in his corner of article just in closing to open it up for questions we're thinking about conducting a webinar in July or August again to talk about a number of different things but to prepare for seating in the fall some of the stuff we'd like to probably share that is we're going to need quite a bit of new data when we start a trial research with P, Dacium chloride and sulfur and so we're going to share some of that I also want to share some information on some of the no-till rotations that are going on around the country this is just a slide from the CCSP firm that is kind of jointly led between George and Christy South Dakota and Southeast North Dakota and what you have there is blue lines is the yield for corn in a corn-corn rotation where the corn is stripped-tilled the second bar, the rose-colored bar is a wheat-weed, a spring-week winter-weed and then corn following that and in a strict no-till setting until and then the third one, the yellow bar is a spring-week winter-weed and then corn the winter-weed is stripped-tilled and then the corn is planted into that and then it's a soybean corn rotation where the soybean ground is stripped-tilled and the corn is planted into that and you'll just notice the four-year average I did not approve 2011 because of hail but you'll note that the strippy and soybean stripped-tilled are both very competitive one another over the long term and you'll note that the corn on corn even using the stripped-tilt cannot compete with those two and then the other thing you should point out in 2012 and 2008 you'll note that the corn has done a little better in one year and then the no-till wheat without the stripped-tilt has actually done the best and that's when we're in a drier environment and warmer environment and I think the one thing we should remember is we've been in quite a period of wet years and I'm just kind of wondering if we're not transitioning back to a drier climate and if we do some of the things and some of the practice that we look at we may need to go back and evaluate where we're at prior to this wet period and some of the things we'd like to probably take a look at in the next webinar are some of the rotation impacts on economics and some of the things dealing with rotations on weed resistance I'm going to quit with that and we're going to open it up to questions but we'll wait for some questions and again I'll just remind you that we'll be posting these to the websites and at the South Dakota State folks like us to ship it to them and have them posted on their website we can do that as well a number of the pieces of data in the South Dakota the other thing we did also indicate that we were going to give out a little prize and Joel picked out a number of course and then Scott figured out who the log in was and that was Sue Raisland and I believe Sue is the writer for the farm and ranch guide at Bismarck so Sue will be getting you that little gift later on I see there's a comment there we lost some 10% of the winter weed in our area has emerged what are the hopes for a decent we can Joel and I will both respond yeah that that really is a point of concern because we really don't know what the status of that seed is I mean it's quite possible that it's imbibed and started the germination process and that process will continue as we get into the spring and that seed will obviously so that's not a critical issue it's just kind of how much bigger and how much stand we're going to likely get from a crop that really just started the process of germination in the fall so that would be one scenario I guess we could have a scenario where those seeds set there dry and never did germinate they'll germinate in the spring and then I guess in a worst case scenario they'll act like a winter weed crop that was planted in spring my my sense would be that in most locations we probably had enough moisture to get this germination process started and that we'll have to keep a close eye on the fields as we come into spring and to see if they're survived you know that's one strike against them being lady mergers are in small plants in the fall and and and hopefully we'll have the kind of weather that will allow those things to express themselves and get out of the ground before it gets too late in the season where we have to make some kind of determination for the germination of the crop and plants on this but I think generally we would say that it's not a hopeful situation that often we have successful in the fields the plant in the fall really didn't emerge completely in the fall but we're able to get it started and then develop into spring I just comment I've been working with winter weeds since 1977 and it seems like one location every year either with research or with my actual fields and one of our farms as well we would have a location someplace where winter weed either was underneath the soil surface or slightly above the soil surface but so much of the whether it makes it or not depends obviously over winter but this period we're in right now if we can get some moisture to root at that surface get the crown is still alive anyway there's still a very good chance that this crop will make it I think we've only lost one research plot since 1999 due to poor emergence and we've had quite a few of them that were hit above the soil surface or half a leaf to leaf stage growth hopefully completely discouraged by it I guess the other thing I'd encourage you to consider is the fact that if you're dry and you take this crop out what crop are you going to plant in a crop is that crop going to have any better chance of making it so I'd encourage you particularly in those areas where you don't have any subsoil moisture to give this crop a little bit of time before you get too anxious oh okay I just want to one comment if you're seeing mold on the plants is probably it so that is generally a pretty good sign that that plant has succumbed what was the next one 32 degrees the sun started to grow Joel says 32 degrees and then I agree with that as far as fertilization I'm not worried about fertilization at all if you've had that seed in the ground my guess says there's been enough moisture for that seed as well that's all it takes then once it gets cold again then the fertilization process is taken care of when you were talking before there and then will that be the next question seed fertilization as far as how long is the temperature required to be cold again Joel I can't remember what the time period is do you know it's probably about Joel is saying it's about a 30 day period that you need for that cold one of the things that you can do is if you go to our website or the VU Canada website or this is just catch one there's a there's a really good section on cold and fertilization and I would guess that NDSU and SDSU probably have that in their materials as well someplace I just bear in mind it doesn't have to be cold Joel pointed out and then that's true it doesn't have to be below freezing for the fertilization to occur it's just temperature to cool and then it's going to serve and then Becky actually answered that Aaron answered so then Evan just popped it in okay the next question from Evan is that when we planted into broken CRP and am most concerned with the volunteer grass mostly Timothy what herbicides would you recommend Joel how to normal you know grass Joel's responses you know if it's your animal your winter annuals or your annual grasses you know we've got some tools to select from but if they're cranial which I think Timothy is and I'm not familiar with control on Timothy but my guess is you probably don't have much choice in terms of that control but I tell you what if you wanted to go to our website and drop me an email Evan I'll do some research on that and try to get back to you we think we may have missed the question here I'll get to the ice question here in a couple seconds I can't remember that was that the person you went to yep nope that was the first one ice okay ice can have a very detrimental effect particularly as we get closer to breaking dormancy as that plant is needing more oxygen you get a layer of solid ice over top of that plant and it stays there for probably four to seven days it can actually cause desiccation and the most the worst situation with these surfaces is probably a little dry and you get some melting going on and then you get a solid layer of water around that crown and all the way to the surface of the soil and that becomes probably the most testimonial yeah so it's not what you'd call typical winter kill this would be ice encasement it's very deadly there's nothing you can do about it I mean it'll doesn't take long to kill the plant but it's common except in your low spots typically that you would have your whole field covered with ice but it's yeah it's anytime from now until things get too big to be iced up ice encasement can be a real lethal kind of scenario one of the things we've experienced is that if the ground is warm underneath the ice layer that ice can actually granularize particularly if you've got a snow layer above the ice and sometimes it will granularize fast enough that there'll still be enough oxygen movement or if you've got stubble sticking through that ice that can also act as a conduit for oxygen as well and that can help well I think we're going to wrap up once we have a quick question thank you folks for attending looks like we had pretty close to 70 folks on and I think there were some groups in the sessions so if you find us an effective way to communicate some timely issues let us know we'd also appreciate feedback on the type of information you'd like to see in these webinars so thanks again for your participation thank you very much


Hello and welcome to JSA TV Live. We are the live streaming news source for DataCloud USA here in sunny Austin, Texas. I'm Keeley Dorian and joining me right now we have Kurt Friesen, he is the director of North America for the International Data Center Authority or IDCA as you might be better known. So welcome Kurt, welcome to JSA TV. Thank you so much, we're thrilled to be here. Well, we hope you're having a wonderful conference so far, how's your experience been and what really attracted you to come here today? Well, I mean, we are kind of in my backyard so that helps but there's a really great attendance here at DataCloud. I'm actually really pleased with the results so far and the turnout, the conversations. Buffy, thank you so much for the panel you hosted yesterday on diversity in the industry which is a big deal but we're at a beautiful resort and we're having a wonderful time. Absolutely, and absolutely a big shout out to our colleague, Buffy. She did a fabulous job hosting not one but two panels but let's talk just a little bit more generally about the IDCA and congratulations, I hear that you're newer to the organization so congratulations on that but what are some of the exciting things that you guys do and are working on? Sure, yeah, it's about week two for me so I'm still trying to fully grasp all of our capabilities and our reach just internationally which has been really impressive so far. I'd say right now our flagship product is our facility audits and certifications. They're really designed to identify weaknesses and the strengths of a facility as well then recommend optimum revenues for the operations and the infrastructure. We do audits on design and build and operations. We do certifications for the entire data center facility itself. We do cloud certifications and we even do certifications on the IT and the application level so pretty robust suite of services that we offer to the industry. And you've been having a lot of really great conversations lately before we sat down over here you were letting me know you were just speaking with quite a few international embassies to talk about putting together some more of those solutions internationally. Yeah, in fact, just last week I was in DC where the IDCA's headquarters is just outside of DC in Rockville, Maryland. And on Thursday we were hosted by three different embassies including Oman and Hong Kong and Malaysia and the point of that was to open a dialogue and a discussion on how the IDCA can provide some strategic consulting to assist in digital transformation for some of the developing sectors of those countries which we've done in the past as well. Definitely important conversations to be having right now is we're just diving further and further into this fourth industrial revolution so we're just excited to see what you guys do and where everything is going. Any sneak peeks of things to come on the horizon that you can share with us right now? Yeah, absolutely. So I think it's exciting to announce it that we're finally going to be doing in-person training again, I think we're pretty much out of the woods. I'd like to say. And so I've identified the markets that we're going to be doing that in over the next 12 to 18 months. The schedule will be released shortly. The markets are San Jose and Phoenix and here in Austin, we're also going to be in Chicago and Atlanta, New York and Loudoun County, Virginia. The idea also is to ideally host these trainings at Colo facilities in these markets. It really doesn't matter which ones. Ideally we want to be able to have those in the facilities so we can provide hands-on training in the data center itself. Kind of a call to action for all the Colos in those locations. Feel free to reach out to me. But you can probably expect me to be calling you within the next few weeks to discuss that anyway. So we've been forewarned. Where can people just keep an eye out on the schedule for those trainings or if they just want to learn a little bit more about IDCA, where can we go? Yeah, we'll be announcing that on idc-a.org. Other announcements to come too will be we're rolling out a membership platform over the coming weeks and I've already started planning a mega conference that's going to be within the next 18 months as well. So that's idc-a.org or Curtis at idc-a.org. Well, Kurt, thank you so much for joining us here at both at Data Cloud USA and then of course on JSA TV Live, we appreciate you being here. So thank you and thank you to our viewers for tuning in and as always, happy networking.


All right. So the setting for this talk is encrypted outsourced storage. So imagine you have a client that has some key that I've denoted here by K1. And it encrypts large volumes of data, a bunch of messages, before uploading them to some outsourced storage service, perhaps a cloud service or some backup. And because we're using encryption, we're worried about confidentiality, particularly of our messages. So we don't want to trust the encryption keys or other information that can be used to drive message data to the storage service. But we do trust the storage service to store our data for us. One thing that we would like in these settings is the ability to do key rotation. So given our key K1, we can generate a new key K2 for a second time period, take all of our ciphertext encrypted under K1 and somehow convert them to ciphertext, which are encryptions of the messages under the new key K2. So key rotation turns out to be a pretty important property in practice, most pragmatically because there's a variety of regulatory regulations that require periodic key rotations. So in the credit card industry, the PCI DSS standard requires this, say, for encrypting credit card data. More generally, you might want this in the context of post-compromise cleanup. If K1 was exfiltrated or you had concern that it might have been exfiltrated at some point, you'd like to rotate to new keys. And there's plenty of other good reasons why key rotation is important. So much so that major companies, when they build the encryption APIs for their customers, include key rotation functionality and workflow specifically to support doing this efficiently. So how do we do key rotation? Well, there's a couple of obvious but unsatisfying approaches. The first and most obvious is just to send both keys K1 and K2 up to the storage service. They can decrypt and re-encrypt stuff. This isn't satisfying because obviously we've exposed the keys to a location where we would not like it to be exposed to. Second trivial approach is just download all the ciphertext and do the re-encryption locally on the client. But there's this obvious performance concern that if you have large amounts of data, say terabytes of data, this is going to be prohibitively expensive in terms of performance. So in practice what people do is use what we'll call the authenticated encryption or a hybrid approach. And that just means that we're going to have an encryption that's like two parts, right? The first part is going to be an encryption under K1 of a data encryption key that we'll label as x. And the second portion will be an encryption of the message under x. So sometimes we refer to these as key encapsulation mechanisms and data encapsulation mechanisms or chem-dem style constructions. So this is nice because when you want to do a rotation, then you can just do a rotation by re-encrypting x. So you choose a new key K2, you just go fetch this short header, this chem ciphertext C1 star, and then decrypt that and then re-encrypt under the new key K2. And this is indeed what's being offered right now by these APIs I mentioned earlier. But there's ultimately a little bit unsatisfying. In particular, the data encryption key x never changes. And when I first started thinking about this problem, it was actually because an Amazon engineer came and said, hey, it's a little bit weird that we have these key rotations that aren't actually rotating all of the secrets underlying the ciphertext. So motivated by that same, I think, observation, there's a nice prior work by Bonet, Louis, Montgomery, and Ragnathon, or I'll refer to them as BLMR. And they introduced this idea of updatable encryption to achieve this type of key rotation where all secrets are changed. So they also use a chem dem style construction where they have an encryption of a dem key under using some kind of standard symmetric encryption. But then the data encapsulation portion is a little bit unique. They use what's called a key homomorphic PRG or super random generator that has some special properties. So g takes a seed x and maps it to a group element in a way that has this additional homomorphism property that you can take g of x plus g of x prime for some other seed x prime. And this is equal to g of x xward x prime. And in turn, you can build these from key homomorphic PRFs. And in fact, the BLMR paper was primarily about how to build key homomorphic PRFs in the standard model. And the updatable encryption was just like one component of that much broader paper. So do a rotation now. We can do something interesting, which is that you get back this type of c1 star. You can use that to recover x. You can sample a new data encapsulation key x prime and then send back to the server now a new header c2 star plus this delta token, which is the xor of xxward x prime. And the server can then kind of rotate the data encapsulation key by adding to the portion of the cybertext c1, this g of delta. And by applying the homomorphism property, you see that c1, this is plus g of delta, is indeed equal to g of x prime plus m. And so we've effectively rotated all the secrets. So that's nice refreshes everything. It has low bandwidth cost because c1 star and c2 star and delta are compact. But it requires quite a number of exponentiations because you're using asymmetric crypto mechanisms underneath these key homomorphic PRG. And I should mention also that they focus primarily on IDCPA style encryptions. They weren't worried about authentication or ctext. And so they're just using IDCPA encryption for this. This will be important in a few minutes. So the status before our work on key rotation is that we have these naive schemes that are ultimately unsatisfying. We have a scheme that's used in practice that has had no formal security analysis. And it's not exactly clear what security this achieves. And in particular, it wasn't really clear what we forego by not having complete rotation, like what type of attacks arise because of this. And then we had this nice work by BLMR15 that targeted chosen plaintext attack security. And they provided a notion up IDCPA that lifts IDCPA to this key rotation setting. And also a notion of ciphertext independence that I won't come into too much details on, but tries to capture this idea that you're refreshing all the secrets. So we looked at this and saw, well, one, it's clear that we can probably achieve stronger security notions than what they are achieving. We wanted to also treat authentication. So we need in practice not taking encryption, not just IDCPA security. And there was also a subtle bug in the proof sketch of up IDCPA from the BLMR15 scheme that I just showed. And so we wanted to fix that as well. And finally, there's a question of whether these schemes that use more expensive operations can be made practical, or is this really going to be too prohibitive in practice? So in our work, we give a treatment of key rotation for symmetric encryption, including authenticating encryption, and introduce three new security notions. An up ID notion that's stronger than BLMR15s, a C-text notion that captures authenticity goals in this setting, and then a so-called re-encryption indistinguishability notion that is in our, our belief is a bit more intuitive than the cyber-text independence notion, and it also captures a much broader class of attacks. And then we use this to analyze both old and new schemes, and perhaps most noticeably introduce two new schemes, one called KSS that doesn't achieve up re-encrypt security, but is very fast, and another re-encrypt, which is a variant of the BLMR scheme that repairs the issues from before, but also extends it to meet our stronger security goals. Now, sort of embarrassingly, just last week, Joseph Yeager found a bug in some of our proofs for up-C-text, and this actually invalidates the security of the schemes for KSS re-encrypt in the context of C-text, as given in the camera ready. So that's kind of a bummer, but Joseph's very nice to point this out to us. We have fixes for the schemes, and are working on a write-up qualitatively. It shouldn't change the result takeaways from the paper, but we'll be putting that up on your print very shortly. And for that reason, I'll be focusing just on the CPA kind of portions of our work. Yeah, didn't mean that to be a joke, but I can see why that's funny. And also, because I didn't have time, that's the real reason, yeah. Okay, so we'll go through these each in turn. So to fix some notation, an updateable AE scheme is, you know, combines the basic three algorithms that we're used to, key generation, encryption, decryption, with a re-key generation algorithm that takes two keys, KI, KJ, and a ciphertext header CI star, and then generates a new, an update token that can then be in turn used with a re-encryption algorithm to rotate the key underlying a ciphertext. And this kind of gives us the right syntax semantics. And I say this is building off the BLMR formalization as well. So you can encrypt something, you can generate a re-key token using it, use re-encryption, and then successfully decrypt the resulting ciphertext under the key to which it was rotated. And we have a formalized correctness conditions for all this in the paper. In terms of confidentiality, we introduce a new kind of class of definitions all based on a relatively complicated, at least looking, security game called up IND. This is a kind of left or right indistinguishability notion for chosen plaintext attacks.  In fact, there's two sets of keys, ones that are going to be uncompromised and then ones that are actually explicitly handed over directly to the attacker. And then the goal of the adversary is to, you know, query a challenge LR oracle here at the bottom, with two messages to one of the uncompromised keys and get back an encryption of one of the two messages chosen at random and try to figure out what this bit B is. The, additionally, the adversary has access to all these other oracles, like a regular encryption oracle to get examples of encryptions that aren't challenge encryptions, re-key generation and re-encryptions. Now we have to be very careful here to avoid trivial wins, right? If you query the LR oracle on an uncompromised key, but then immediately you can go get a re-encryption of that ciphertext to a compromised key, one of these ones that's handed to the adversary directly, there's going to be a problem, right? You're going to win trivially. So we spent a lot of time trying to figure out exactly how to formalize what are valid and invalid queries that should be allowed to re-key gen and re-encrypt. And so we give these predicates, these invalidity predicates that define exactly that. We spent a lot of time trying to make the most permissive invalidity predicates that we could come up with. The BLMR confidentiality notion actually ends up being captured in this framework. We just have much stricter invalidity procedures that rule out any queries to compromised keys. And additionally, they don't return a ciphertext header on an invalid re-encryption query. This last thing turns out to be something that was kind of interesting to us because it surfaced a compromised scenario that we hadn't thought of before, and in fact, allows showing that in our model, these things like A hybrid don't even meet this up IND security notion. So let me just go over that very briefly. So remember, our A hybrid is just this chem-demp thing where we encrypted a data encapsulation key X under our key K and then the message under X. And in this context, our adversary can do the following. Query, the left-rights oracle to get a challenge ciphertext. Query, a re-encryption now to re-encrypt this ciphertext to a compromised key, so T plus one. So this is one of the ones that's given to the attacker. And at this point, the invalid procedure will say, oh, this is kind of an invalid query because you're rotating a challenge ciphertext to a compromised key. But because we're being very permissive, we're gonna give back the header C, in this case, C, T plus one star. Okay, but that's just an encryption under K, T plus one, and for this scheme of X. And so we have the key there, so we can just decrypt and get back X and then recover from C1, M sub B, and win there. So this ends up being a sort of, perhaps in practice esoteric compromise setting because you need a certain combination of values, but it was interesting to us that this got surfaced from exploring these definitions formally. And it turns out that we can actually achieve this security, achieve security and avoid these types of attacks by a pretty simple change to AE hybrid. So that change is what we call a chemdem with secret sharing. The basic problem with the security in our model from before is that if you get this compromised header, header for compromised key, that's enough to reveal the data encapsulation key completely. And so what we can do is prevent that by doing a kind of secret share of the data encapsulation key across the two portions of the ciphertext. So now we sample an X and a Y. We store inside the key encapsulation an X, X word Y and store Y with the other portion of the ciphertext. And this is just like I said, a simple secret sharing scheme. When we do rekey generation, we can get back the header, decrypt it to get back this X or X, X or Y. We can sample new Y prime, kind of refresh the secret share by X or Y prime into X, sending Y prime as well over to the storage service and refreshing on that side as well. So it turns out we can prove that this is up IND secure and it really has a very small overhead compared to A hybrid. It's just the addition of these small XORs that are, you know, say 128 bits. But note that the data encryption key here is still never rotated, okay? So we're still kind of in the same fundamental place that X is never rotated. And this begs the question of what we're giving up basically by having schemes that say are just up IND secure and not refreshing all of the secrets underlying ciphertext. So we spent a lot of time trying to figure out what are interesting attack models that can take advantage of this lack of refresh of the data encapsulation key. It wasn't at all clear to begin with. And we came up with a few different things and I'll explain just one exfiltration attack scenario that seems to be important for this property. So imagine you have in a time period one and we'll just do this in the context, A hybrid is a little bit simpler, but the same thing applies to KSS. In the first time period the attackers say compromises both gets access to both K1 as well as a full ciphertext. And at this point, perhaps because he's under in this time period some type of constraints about how much data he can exfiltrate, he can't exfiltrate the whole message, but he can get out some small secret that allows him to output the data encapsulation key X. And then later if we do a rotation, say cleaning up after that compromise and moving to a new key K2 and the adversary later on gets access now just to the ciphertext, but not K2. We've done better jobs securing our key K2. Nevertheless, this X value is still enough to recover the message, right? Because we haven't rotated that key. So this type of, we'd like to have security models that deal with this type of attacks as well. And so we introduce this re-encryption indistinguishability notion that speaks to it. And it's basically a strengthening of, or it's stronger than the ciphertext independence notion from the LMR. And I'll just again give some intuition about what it's doing for us. So it's again using some type of game to formalize security, and instead of having left to right challenge oracle that you query two different messages to, we're gonna have a left to right re-encryption oracle that we can query two different ciphertext to. And the idea is that the attacker shouldn't be able to tell which of the two ciphertext was actually re-encrypted, okay? The intuition for why this is, and we have all the same problems in validity predicates, and there's other oracles which I'm not showing here, the re-key generation and re-encryption and encryption stuff. So the intuition is that basically we wanna capture an idea in which, I don't know what that was, in which the ciphertext basically from one time period is useless to an attacker in the next time period. And this captures that, because the attacker can't even tell which ciphertext was used from one period in the rotation. And in particular, it rules out these exfiltration attacks. So the question is can we then achieve both up IND security as well as this up re-encryption security? And the natural starting point for that is the BLMR scheme that uses this key homomorphic PRG. But as I mentioned briefly before, there's a bug in the proof, and it turns out it's not even up IND CPA. And this turns out to be somewhat easy to fix, but technically it was kind of interesting understanding this bug, so let me go over it very quickly. So called the BLMR scheme's unprovable, the BLMR scheme is using this chem-demp style thing with this key homomorphic PRG. And this allows updates by exploiting the homomorphism properties of the PRG. As they put in their paper, basically a theorem that a high level is saying that if E, the chem encryption is IND CPA and G is a secure PRG, then the scheme meets this up IND CPA security. So it turns out this is problematic, in particular because in the security games, both in their paper and in ours, the adversary gets access to re-key generation oracles, which means that in particular, they can mount a kind of chosen ciphertext attack against the underlying chem encryption E. And so IND CPA doesn't seem like it should be enough to prove security. So that was easy to understand, but trying to figure out whether this is actually insecure took a lot of work, and instead, we weren't able to come up with a direct attack showing that this is insecure for some instantiation of E, but what we were able to show as a relativized result that if you could give a proof of this up IND CPA security just from the IND CPA security of E, then this would imply a proof that this particular construction E is, it's IND CPA security implies that it's actually circular secure. There's been a long line of work on circular security and showing like negative results about IND CPA implying a circular security. Those don't directly apply because we have a very special form of E in our result, but nevertheless it seems like a lot of evidence that you're not gonna be able to prove something strong here. Okay, so it's easy to fix up that one issue because we can replace IND CPA chems with an authenticated encryption scheme, and in addition we add other features to the BLMR scheme to arrive at this re-crypt scheme that achieves our stronger security goals as well. So using AE for the chem prevents this type of modeling issue that came up in the proof or the attempted proof of the previous BLMR scheme. We also do the same type of technique as we did for KSS which is the secret share, the data encapsulation key across the two components of the cipher text. And when we do a refresh we now need to not only refresh the key X, but also the secret share Y. So I won't go into details, but it turns out we can show that this is both up IND and up re-encrypt security, so in words this means that we get this stronger confidentiality even with access to these re-key gen and re-encryption oracles, and that the cipher text in a similar kind of attack setting is basically useless, cipher text from one time period under one key are kind of useless to attackers moving forward, so you get this very full security. So finally the last question that I had was whether we can make these things performance enough in practice. We did a bunch of work to implement re-crypt in a highly optimized way. We used, underlying it, the Naur Pinkett's Rheingold key homomorphic PRF, which is this like random oracle model construction that also uses a DDHR group. For that we used a curve 25519. Put together this basically allows us to encrypt L-bit messages in requiring roughly about L over 248 exponentiations, and rotation requires about the same. So the high level takeaway is this is by symmetric encryption standards and cruciatingly slow, and it's about a thousand times lower than the use of like AASNI with ASGCM, which is what you can instantiate a hybrid or KSS with. So for short messages, you can still do this in milliseconds, but for large bulk data this seems prohibitive at this point. And it's kind of a cool open question whether this is kind of fundamental to get this key rotation property. We really need algebraic properties and we can prove that you can't do better. Or maybe if not, then we can come up with something a bit faster. Okay, so to summarize, we provided a formal treatment in depth of key rotation for symmetric encryption. We introduced a bunch of new security notions that strengthen on the prior work and investigated these using a bunch of new and old schemes. And the high level takeaways, those are fast and the other ones are slow. And finally, we have this embarrassing bug in our C-text of proofs, and so please stay tuned for a fix to that, which we'll be posting shortly. Thank you very much.


Hey, don't change your diet.  Here's why protein and fiber are the most satiety producing components of food. In other words, if you, your protein and fiber first, you're less likely to overeat or to put it differently, you're more likely to eat less calories simply by doing this is one of my favorite because almost every client I ever trained had a chip or bread addiction. And that was almost inevitable that they would ask, yeah, but Adam, why I love bread or I love chips. And my favorite thing to do back to them is be like, I'm not telling you can't have it, but we just got to make sure we go get your protein first. So that's all I want you to do.  All I'm saying is I need you to go get me my 40 grams of protein in that meal first. And they'd be like, really? I can have my bread. Yes. And they always, they report back this, you know, I ended up getting to that point. I'm like, I didn't even care. I didn't even want it. Whatever you eat, keep eating. Just change the order of it and then watch what happens. And it typically results in some slow fat loss.


Hi, and welcome to the session. My name is Rashi and I am going to help you with the following question. Question is, solve the following pair of linear equations by the substitution method. First equation is, x minus t is equal to 3 and the second equation is, x upon 3 plus t upon 2 is equal to 6. Let us start with the solution now. First of all, we will rewrite the equations given in the question and name them as 1 and 2. From equation 1, we get s is equal to 3 plus t. Let us name this as 3. Now, we will substitute the value of s in the equation number 2. Now, substituting the value of s in 3 in equation number 2, we get 3 plus t upon 3 plus t upon 2 is equal to 6. Now, this implies, we take the calcium equal to 6 and 2 multiplied by 3 plus t plus 3t is equal to 6. It is equal to 6 plus 2t plus 3t upon 6 equal to 6, which further implies 6 plus 5t is equal to 36 or 5t is equal to 36 minus 6, 5t is equal to 30 or is equal to 30 upon 5 equal to 6. So, t comes out to be equal to 6. Now, we will substitute the value of t in the equation 3. Substituting the value of t in equation 3, we get s is equal to 3 plus t, which is equal to 3 plus 6 or this implies s is equal to 9. So, our required solution is t is equal to 6 and s is equal to 9. Substituting t is equal to 6 and s is equal to 9, we can verify that both equations 1 and 2 are satisfied. So, this completes the session. Hope you understood the session well. Goodbye and take care.