Thank you very much. Good evening. My name's Andrew Donoghue. I'm the managing director of Blue Packets. I'm here this evening to talk about managed services and the cloud. I'll quickly cover what I'm going to run through. So now's your chance to go to the toilet. First of all, will this presentation be useful for you? What are managed services about trusted configurations and system life cycles? A quick introduction to cloud computing, about cloud computing and managed services, getting to the cloud and your systems in the cloud. First things first, should you be watching this presentation? If you need your IT systems to be working, the answer is yes. Going back 10, 15 years ago, IT could be down for half an hour or an hour. Life went on. You go and do your paperwork, shuffle things around. Now your paperwork is your IT system. If it stops, everything inside your organization is probably going to stop with it. There are a few exceptions to this, I should note. There are some people who can get away with their IT for half a day or a day, but those businesses are becoming less and less as time progresses. Next thing, what are managed services? Think of these as a systematic approach to delivering IT servicing. It varies greatly from the paper hour model that a lot of you might be used to. So instead of having someone come out for an hour block or two hour block or five hour block to deliver services, it's based on an outcome. So that means the provider can deliver the service in the most efficient manner. As mentioned, often under managed services, specific tasks are undertaken for a set price. So this means things like backup testing, security updates, hardware health checks if you've got hardware on site, reporting, monitoring and general management and perhaps some reactive servicing is bundled in with that price. There's an efficiency dividend here. This means the provider can provide the outcome in the most efficient way possible. They don't get tied up in red tape asking you for permission to spend five or minutes solving a task. They go and solve the task with the problem themselves. That way next month, the problem doesn't exist. They can give a good quality solution and a faster outcome. It also helps solve bill shock too, which is a big one. And this comes down to the old school thinking of fix it when it breaks is no longer good enough. Now get my car serviced every 10,000 Ks or so. Yes, the mechanic makes money out of me along the way, but my car is never ever broken down. I hope it doesn't. It provides greater uptime for me. It's there when I need it. And I don't have any nasty things like the oil running out and downtime because the car's not working. It's a bit of a leap frog, but talking about trusted configurations. So if your ICT provider is giving you advice about what hardware to use and you still need devices, this applies to both on-premise and off-premise in the cloud devices. It's important to listen to them if they're giving good advice about how you connect, what you purchase to get to the cloud. They're a different device and some are very expensive, some are cheap. The cheaper option is always attractive. Often the cheaper options can be have a shorter lifespan, be slower and much more expensive to manage. So while you might have a few dollars right now over the life of the product or the life of the service, it'll probably cost you a lot more. The next question is what to manage because managed services come at a price. So you might have dozens of systems lying around and you might have one that's only used by a few staff. The simple answer to that is if you can't afford it to break, then manage it. If it's going to be too costly to manage, consolidate, move it on. There's a whole bunch of options out there for you. If it's a server or a device running in the corner that only a few staff could use but you can't afford to turn it off, then something's wrong. You can either turn it off or you need to look after it. If it's not worth managing, as I said, get rid of it. And everything will eventually fail. So if you're just waiting on it to break, you're waiting on a disaster and you're better off dealing with it now. Managed services are good at making your systems run a bit faster. Cleaning out your temporary files, running security updates, making sure the experience as a whole is a nice one. The problem is you can get this illusion that your system's gonna run forever. So yes, the provider's doing a great job. Things are working. Things are working. Things are working. Things are still working. There is a point there where software updates, maintenance, and general IT support cannot make that device work forever. Well, that system work forever. Presume sometime it's gonna fail. Don't wait until it's time to fail. Get in early, plan ahead. Even if you don't execute that plan for two or three years, have that plan ready. So when you decide, you decide to move on your terms and it's not a rushed decision because rushed decisions will cost you a lot of money. Cloud computing. Besides a fancy marketing term, perhaps the simplest way I can describe it is a resource that is used outside of your network. So it's something your company doesn't own or operate. It's an IT service provided by someone else. This could be as simple as email, external email, anti-spam, anti-virus scanning, offsite backup, who go all the way through to a complete managed virtual server or software as a service where your application is delivered to you as a finalised product. And this is where the type of service becomes very important. If it's a raw service, as I said, like a virtual server, who is checking your backup and system status? Who is running security updates? Who is going through making sure the latest version of software within that virtual service is applied? Who is looking after the integration and general support? It's working great. It breaks. Who do you call? And do you have a way to manage the cloud services efficiently? So you might have one, two, three, four different cloud providers. There might be applications for this, a virtual server there. If you have a new staff member to start, do you have to add accounts in all those places? Who ties it all together? How much time do you spend adding a user account? Beyond premise wealth has done it quite well now. In most cases, if you have everything in sight, you can add a new user within 5, 10, 15, 20 minutes. If you have multiple cloud providers, how long is the same thing going to take? I should step one, one bit back. That's where the value of a managed provider comes in with a cloud, is actually taking that step and helping you manage part of that process. So instead of you being on your own and trying to get to the cloud and manage it, a managed service provider should be able to tie it all in for you nicely. And if it's not nice in it, it should be able to manage the process for you, document it, and be able to action the request on your behalf. So you've got the cloud, it's outside your office, you still need to have an on-site network. I'll come back to reliability about this. Is it fast enough? There's no point having this great system out in the cloud that's outside of your network if you're stuck on a connection from last century. It's got to be fast, that does cost. It's got to be congestion-free. You want something fast, it's going to be responsive. And even with the NBN and other bits and pieces coming out, there still is latency. The pipe that gets between your business and the outside world is still relatively small. That'll improve over time, but it will take time. What happens when the internet goes down? If your network is heavily reliant on a very fast connection, you may be in trouble. Internet failures still happen. Almost, might be not uncommon, but you can see half a day to a day of outage per year. If you take all the five, 10-minute, 15-minute, one hour blocks put together. If you're reliant on the internet to be functioning for this, that's quite a serious disruption to your time.  That's quite a hit and quite an expense. And make sure you've got a plan in place. So when it does go down, you can get back up and running efficiently and it's not half an afternoon off. You don't have to run back home. Other phones, cloud-based, are they going to work still once the internet goes down? And make sure you test it. Importantly, if you have in-house servers, your data's on the server. It might not be being backed up properly, but you don't know. You've got to make sure if someone's looking after it. But you can see it. It's physically there. As long as your building doesn't burn down, it should be okay. If your data's, if everything's in the cloud, it might be hundreds of kilometers or even thousands of kilometers away. So you've got to make sure you back that up. If you have multiple cloud providers, it is worth engaging a separate cloud provider to back up your data. I can't speak for everyone else here, but if we lost our data and our systems would be in serious trouble, it is worth protecting that data like it is your lifeline. And without it, you'll be in serious trouble. So make sure you've got a plan to back it up. Make sure it is being backed up and make sure that any extended outages can be dealt with. I say it's a very low likelihood, but the impact is massive. So it means you've got to deal with a risk. So in summary, if you need those systems to be working, make sure you manage them. Don't ignore it. The cloud services and cloud offerings are a great opportunity for everyone, both in terms of efficiency and cost reduction, and risk exists both on-site and off-premise. By putting your systems into the cloud, you don't reduce that risk. It's still a risk that's got to be managed, so make sure you look after it. That's it. Excellent. Cheers. Thank you.


Hi, basically random number generators that we've seen that true random number generators are typically produced a bit at a time and random number generators have typically not scaled with Moore's law and we put together the idea of parallelized random number generators with the fact that the noise in CMOS sensors, image like your camera sensors has been widely studied and nobody's been able to get rid of it other than cooling it down. So the idea is can we build a gigabit random number generator out of a standard CMOS sensor? Basically, and this physics messed me up, the idea is that heat forms phonons that vibrate the electrons in the conduction band, from the valence band to the conduction band to create a Poisson distribution of electrons in each one of the pixel values and this amount of electrons in these pixel values increases exponentially with temperature. So the idea is that we can take any CCD sensor that has a raw output, basically adjust the amplifier so that with zero electrons you get something out, a digital number out and as you go up the amount of electrons you go to saturation and then you'll get a Poisson distribution of values. We were able to take pictures and actually take the first pixel of every frame and compare it to the first pixel of every other frame and we were able to calculate the Shannon entropy of all of the pixels in there and we found that in a 16-bit raw picture that there is about three and a half bits of raw entropy and we basically have it shown in a cumulative distribution. We're able to take and whiten it using a basically just about there are many methods in the paper we have yet one more method and we are able to take that result and again something called the die-harder test which is a random number generator. The line that is closest to the diagonal is this random number generator. This is the bad Unix random number generator. This is the better random number generator on Unix, one that blocks. This is the Mercine twister which is considered one of the best random number generators. So we consider the results to be very good and if you get three bits of entropy per pixels 24 megapixels 30 frames per second that's 2.1 gigabits per second of pure entropy. Thank you very much.


Wildlife managers have found two more deer are suspected of being infected with chronic wasting disease in southeastern Minnesota, raising the number of confirmed and presumptive cases in the area to five. The doves were killed within a mile of where the first two deer that tested positive were shot in November, which marked the first appearance of the fatal brain disease and wild deer in Minnesota since 2010. Cases are also rising in Wisconsin and Iowa. If you've enjoyed this segment of Lakeland News, please consider making a tax-deductible contribution to Lakeland Public Television.


I obviously love horses. I always had real horses in my life, but a dream of mine has always been to have a donkey. I've always wanted a donkey. I think I want a miniature donkey, you know, the short little cute ones. I'd love to have a donkey that I could take trail riding. It would just run behind my horse. I've heard that donkeys are more social than horses. I don't know if that's true. I've lived around a couple donkeys. They're very loud. I mean it's like a horse with bigger ears and bigger eyes. What could you ask for? That just makes it automatically even more cute. So that's like two or three years. Pretty much since I started dating my boyfriend, I've said I've wanted a donkey. And I specifically became more intense about this when I saw a picture online of a beer donkey.  And this donkey was wearing like a flower crown and it was adorable. 100% I need that at my wedding. Specifically around Christmas time, I get really intense about it every year. I don't really want anything for Christmas. I just want a donkey. Well this is going to be a lame Christmas because there's no presents shaped like a donkey under the tree. I don't want any presents unless they're shaped like a donkey. A Christmas morning comes around. There's nothing under the tree shaped like a donkey. But my parents did say that two Christmas presents did not come on time. They kind of hinted at a donkey a couple times. It was coming all the way from Israel. The roads were too bad for the present to arrive. Then I was at my parents' house. Turn around, close your eyes. We're going to surprise you with this gift. Okay, turn around. With your eyes closed. With your eyes closed. Okay, open. What is it? Is it shaped like anything? Like five-year-olds. Up on. It's not for riding. Ring cart. Give me the hug. Lift it up. It really shaped like a donkey and I felt so bad for my mom because it would have been the gift under the tree that was shaped like a donkey.  When I unwrapped it, I had an interesting drive home in the back of my main truck. This is not really how you should... I have a house donkey but his ears were really bothering me. My customizing soul said I must customize even my stuffed donkey.  Don't worry, the donkey was under sedation during his procedure. His ears actually turned out so cute. He's adorable with perky ears. He genuinely lives in... He needs a name My parents are hilarious and one day I will own a real donkey, but for now this is sufficient. So the moral of this story is always follow your dreams. If you want something really bad, it may happen to you one day. Not always in the way that you expected, but it will happen.  I'm also hoping I don't have to like use the fake donkey at my wedding. I can say that I got a donkey for Christmas, so that's fun.


Welcome back. So, in the last lecture, we started discussing multistage rockers. We have discussed the nomenclature that we use to represent the performance of multistage rockers. We have also discussed that why do we need multistage rockers, what are the performance improvements that we can gain by going from a single stage to a multistage design. Next, what we will do now is to talk about the performance. We will derive the expressions which represent the performance of a multistage rocket. Before we do that, first let us make the assumptions that we will be talking about. We will be neglecting the lift neglecting the drag and neglecting the gravity that is L is equal to 0, D is equal to 0, G is equal to 0. Now, as for the last few lectures, we have been talking about these assumptions. First of all, lift as we have seen typically works perpendicular to the flight path. So, if lift is non-zero, the vehicle will start to deviate from the intended side path. Therefore, we always like to have lift to be 0, because these are non lifting vehicles. So, therefore, this is not an assumption is actually a practical reality. Coming to the drag on the ground or close to the ground, because the atmosphere is very dense, we will have some drag. But the point is that the rocket vehicles travel extreme distances and as we go up high in the altitude, the density falls rapidly. So, therefore, as we go high and high, the density will drop. Therefore, the drag is also going to go down. So, essentially the drag although towards the beginning in the booster stage is important as we go further up out towards the edge of the atmosphere, drag becomes a very small amount and in the outside the atmosphere drag is practically 0. Therefore, neglecting drag also is something that is a reasonable assumption. And coming to the gravity, gravity is going to be there, but the effect of the gravity once we go to outer space is not very large. But as when we come to space dynamics, we will see that all our mission is actually dictated by gravity. Gravitational force is the most important parameter in rocket propulsion. So, gravity is going to be there, but the magnitude is not going to be very large. So, for practical applications or the initial design, let me put it this way, the initial design when we are designing the rocket initially for a given mission, we can safely neglect the effect of gravity as well. And by neglecting particularly the drag and gravity, our rocket dynamic equation which is a differential equation becomes independent of time. Therefore, we do not have to integrate over time to get the velocity increment. Therefore, neglecting gravity and drag actually simplifies our calculations and then as we have seen for the single stage rocket, the velocity increment becomes a function of equivalent velocity and the inverse of mass ratio R. Now, this was the starting that we have proved for the, we have proven for the single stage rocket. Now, the same thing now can be applicable to a multi stage rocket. So, if I write the same equation for a multi stage rocket, I will write it like this delta u i equal to u equivalent i L n M naught i upon M f i which is essentially equal to u equivalent i L n R i. Here i represents the i th stage of a multi stage rocket. We have discussed the nomenclature in the previous lecture that we have n number of stages, every stage is designated by subscript i. So, i can be 1, 2, 3 up to n depending on the number of stages. So, this is the expression for the velocity increment under these assumptions for the i th stage. So, delta u i then is the velocity increment for the i th stage that is the difference of velocity at the end of burning for the i th stage minus the difference in velocity at the end of burning for i minus 1 th stage or the previous stage. So, previous stage burns it leaves the vehicle with certain velocity and then the i th stage takes over from there and gives an increment. So, that increment is given here by delta u i, u equivalent i represents the equivalent velocity for the i th stage. So, that depends on the specific impulse. So, I can write it here as u equivalent i is i speed i times g e right, where i sp is the specific impulse for the i th stage and g e is the acceleration due to gravity at sea level. This is something that is important this is g e is all sea level only in the gravity term if we consider then that appears as g. So, then with altitude it varies, but here it is only at the sea level. So, the equivalent velocity for i th stage is given like this and then the mass ratio inverse of mass ratio r r i is m dot i by m dot f that is the initial mass of the i th stage divided by the final mass of the i th stage. We have defined all these parameters in the last lecture.  This is my expression for velocity increment for the i th stage of a multi stage rocket. So, now if I have n stages then what is happening is this the rocket let us say is starting from 0 velocity. At the end of first stage it gains a velocity delta u i a delta u 1 end of second stage it gains a velocity delta n 2 like that. So, to the n th stage after the burning of n th stage it gains a velocity given by delta n sub n. So, therefore, the overall increase in velocity is nothing, but the summation of the velocity increment for all the stages. So, the overall delta u is nothing, but sigma delta u i i going from 1 to n. So, therefore, the overall gain in velocity for a n stage rocket is the sum of the gain in velocity in individual stages. So, that is given as like this. So, therefore, let me write the overall delta u now in terms of this. So, this is equal to sigma i equal to 1 to n delta u i and my delta u i is this term. So, this is equal to sigma i equal to 1 to n i s p i g e l n r i that is the expression for overall velocity increment for a multi stage rocket. Now, as we have been seeing so far the parameters that are known sometimes the structural weight will be known such time the propellant mass will be known sometime the payload mass will be known. So, there are different things that are known parameters. So, therefore, although this is the governing equation we may need to write it in different forms. Secondly, when we come to optimization you will see that we will optimize let us say with respect to the payload fraction of different stages or let us say with respect to the structural coefficient of different stages. So, therefore, for those cases then this equation has to be written in terms of those variables let us say payload factor structural coefficient etcetera. So, what we will do next is this is our basic equation for velocity increment. We will just rewrite is this equation in terms of the other defined parameters that we have defined. What are the parameters we have defined? We have defined lambda, we have defined epsilon, we have defined l etcetera. So, we will try to express this in terms of this parameters. So, now, let us look at this term r i as we know that this is the inverse of our mass fraction or mass ratio. So, this now r i we will represent in terms of this parameters lambda, epsilon and l because these are our optimization parameters. So, first of all let us look back at r we have seen that r is equal to 1 plus lambda upon lambda plus epsilon. Now, this is for a single stage rocket. So, therefore, for every stage of a multi stage rocket also this expression is valid. So, we can write r i equal to 1 plus lambda i plus lambda i plus epsilon i. Where r i is this term inverse of the mass fraction for mass ratio for the i th stage lambda i is the payload factor for the i th stage and epsilon i is the structural coefficient for the i th stage. So, then going back to our definition of payload factor how did we define the payload factor? Payload factor is the payload mass divided by initial mass minus the payload mass that is all the mass except the payload.  Now, if we use this definition for the i th stage of a multi stage rocket then we will write it as lambda i m l i upon m naught i minus m l i. Now, comes the interesting part. So, this is the payload factor for the i th stage which is the payload for the i th stage divided by initial mass for the i th stage minus the payload for the i th stage. Now, from our discussion in the previous lecture what is the payload mass for the i th stage? As we have discussed in the last lecture this is the total mass of the i plus 1 th stage because this is something the i th stage delivers. So, therefore, this m l i is the total mass or initial mass for the i plus 1 th stage that is the next stage next upper stage.  So, this is the payload factor for the i th stage is the initial mass for the i plus 1 th stage divided by the initial mass of the i th stage minus the initial mass for the i plus 1 th stage. So, therefore, this will be defined only up to n minus 1 because for the n minus 1 th stage this is m l, but if I put it as n th stage sorry it can be defined up to n th stage. For the n th stage this is the overall payload m l. So, for the n th stage lambda n is equal to overall payload m l divided by the initial mass for the n th stage minus the overall payload sorry. So, the payload factor for the n th stage is given like this. Next let us look at the structural coefficient. Now, so far again the structural coefficient we had defined for a single stage. Now, when we come to the multi stage then we define the structural coefficient for every individual stage. So, next let us define the structural coefficient. Structural coefficient for a single stage rocket was defined as the structural mass of the rocket divided by the structural mass and the propellant mass. That was our definition of structural coefficient. Now, we know that the overall mass is the sum of structural mass plus propellant mass plus the payload mass. Therefore, the sum of structural mass and propellant mass is the initial mass minus the payload mass.  This is for a single stage rocket. Now, we use the same definition for a multi stage rocket. So, we define the structural coefficient for the i th stage of a multi stage rocket. So, that will be given by a subscript i which is equal to m s i divided by now m naught becomes m naught i minus m l i where m s i is the structural mass of the i th stage, m naught i is the overall mass or initial mass of the i th stage, m l i is the propellant mass sorry the payload mass for the i th stage. Once again going back to the discussion here the payload mass for the i th stage is the initial mass for the i plus 1 th stage. So, therefore, this is equal to m s y m naught i minus m naught i plus 1. So, this is the definition of then structural coefficient for the i th stage. Next let us define l, l is our propellant payload mass fraction. So, payload mass fraction we hand define this as m l upon m naught for the single stage rocket. This is payload mass fraction, this is the fraction of payload mass with respect to the overall mass. This is payload factor, lambda is payload factor these two are different. So, as you can see here lambda is defined as the payload mass divided by all the mass except the payload. Payload mass fraction is the fraction of payload in the total mass. So, lambda and l are two different parameters. So, lambda is called payload mass factor this is payload lambda is called payload factor this is payload mass fraction.  So, that payload mass divided by the total mass this is for a single stage rocket. So, once again if I use this definition for a multi stage rocket then I represent this as l i.  So, this can be written as m naught. So, now if I recap what we have done so far is we have defined r i for a multi stage rocket we have defined lambda i for a multi stage rocket we have defined epsilon i for a multi stage rocket and l i. These are the four parameters we have defined so far in this lecture and we have defined most of them as functions of m naught i m naught i plus 1 and m s i. See these are the three masses that has been used. So, we have defined the this four parameters for multi stage i s stage for single stage for multi stage rocket in terms of these three masses the structural mass of the i s stage the initial mass of the i s stage and the initial mass of the i plus 1 s stage based on this we have defined now all these parameters. Let us now take a further step write one more relationship here we have one relationship relating r lambda i and epsilon i in the last class we also derived one relationship relating r l and epsilon. So, let me first write that expression for a single stage rocket when I will write that for a multi stage rocket. For a single stage rocket in the last class we had derived this expression that r equal to l 1 minus epsilon plus epsilon this is one expression we had derived in the last class for a single stage rocket. Now, if I use it for a multi stage rocket then for the i s stage I can write r i equal to 1 upon l i 1 minus epsilon i plus epsilon i. Now, if I take this expression and then go back now to our expression for delta u and this is one another expression was 1 plus lambda i upon lambda i plus epsilon i these are the two relationship that we had. Now, go back to our expression for delta u for the multi stage rocket we have shown that the overall velocity increment is the algebraic sum of the velocity increment of the n stages. So, this was equal to sigma i equal to 1 to n delta u i and delta u i is equal to u equivalent i l n r i and then u equivalent is equal to i s p. So, I can write it as i s p i g e l n r i. So, this is one expression let me write it as equation 1 now we can replace r i by this. So, in the same equation now we can replace r i by either this expression in terms of l i n epsilon i or we can replace it in terms of lambda i and epsilon i. So, therefore, I can get another expression for delta u which will be equal to sigma i equal to 1 to n i s p i g e if I replace r i by this then this is equal to l n by 1 upon l i 1 minus epsilon i plus epsilon i let me call this equation 2. So, here in this what we have done is we have replaced r i by this expression for l i n epsilon i or we can also replace r i by this expression in terms of lambda i n epsilon i.  So, this three equations that I have written here are actually same only thing is that different representation of the various parameters depending on what are given to us we can either estimate r or l i epsilon i or lambda i then these are essentially the equivalent expressions and this becomes handy when we go for optimization. So, this three equations we will be using for optimization purpose any one of them. Before we proceed further now we will try to look at relationship for l i, l i is a very important parameter that is the payload mass fraction is a very important parameter for multi stage rockers. So, let us take a closure look at the payload mass fraction. So, next we will look at first of all the overall payload mass fraction. This is the overall payload mass fraction for the entire rocket entire multi stage rocket. So, it is given by l.  Now, in the nomenclature what we have seen is the actual payload actually is the payload for the nth stage also. So, therefore, this m l can also be written as m l n. So, it can be written as m l n and the total mass is the initial mass for the first stage. So, I can write it as m naught 1. So, then from this discussion m l is the payload mass for the nth stage divided by the initial mass for the first stage. Now, I can write this as the initial mass payload mass for the nth stage divided by the initial mass for the nth stage. Then the initial mass for the nth stage is my payload mass for the n minus 1th stage. So, I can write it as m naught n minus 1 divided by the initial mass for the n minus 2th stage divided by the initial mass – no, just a second. This is the initial mass for the nth stage which is the payload mass for the n minus 1th stage. So, let me just re-do it. This is the payload mass for the nth stage divided by the initial mass for the nth stage, and we have said that initial mass for the nth stage is the payload mass for the previous stage. So, this is the payload mass for the previous stage divided by initial mass for the previous stage and then we continue. So, now this becomes the payload mass for the n minus 2 s stage and then the initial mass for the n minus 2 s stage and we continue like this till we come to the first stage m 0 2 is the initial mass for the first the sorry initial mass for the second stage which is also equal to the payload mass for the first stage. So, we continue like this till we come to the first stage. So, now if I look at this equation and look at the definition of L i, L i is the payload mass fraction for the i th stage which we have defined as m naught i plus 1 upon m naught i we have defined it like this. So, now let us look at this term what is this m 0 2 initial mass of the second stage which is the payload mass for the first stage divided by m 0 mass which 1 which is the initial mass for the first stage. So, therefore, this is nothing but L 1. So, this is equal to L 1 then multiplied by L 2 continues till if I come to any stage in between it will be L i into what is this the payload mass for the n th stage divided by the initial mass for the n th stage. So, that is L n. So, that is payload mass fraction for the n th stage. So, now what we see here is the overall payload mass fraction is essentially the product of individual payload mass fractions. This is a very important observation this gives us as a constraint and it is true no matter what. So, this is a constraint with which we will be working. So, we can write as L is equal to product of i equal to 1 to n L i. This is a very important result. So, let me call this equation 4 when we are using this equations when we are using this equations L i is appearing here. Typically the overall payload mass fraction will be a known quantity from there we can estimate L i. I will come to that later or when we go to optimization there will be a specific relationship which can be shown. So, therefore, no matter what by the way for a multi stage rocket this expression is always valid because of the fact that the payload for the one stage is the initial mass for the next stage. Therefore, this equation is always valid. Now with this then let us now solve a problem for estimation of essentially velocity increment for a particular rocket with particular given conditions. We will take a very simple example later on when we do optimization then we will be go for little more complex problem at a very simple problem. Essentially what we are trying to do is use this equations to get some information. Let us consider a three stage rocket in free space. So, essentially first of all what does this term free space means that G and D are 0 gravity and drag are 0. For this three stage rockets we are supposed to find out the velocity increment delta V. The conditions given are A that the structural coefficient for all the stages are same that is epsilon 1 is equal to epsilon 2 is equal to epsilon 3 that is equal to 0.1. This is a given condition. Secondly what is given is that the ISP values is given that the ISP value for the first stage is 250 second, ISP value for the second stage is 300 seconds and that for the third stage is 350 seconds. These are the three values that are given. It is also given that the overall payload mass fraction L is equal to 0.01. Another condition that is given is that the payload mass fraction for every stage is same. These are the conditions that are given. We have to get the velocity increment for this rocket. First let us come to this L is equal to 0.01 which is the total final payload divided by the initial mass and we are given L 1 equal to L 2 equal to L 3. First what we do is let us get these values. What are the values of L 1 L 2 L 3? For that we use this equation. What we see here is that first let us write L 1 equal to L 2 L 2 L 3 is equal to L i. Then from that equation L equal to pi i equal to 1 to n L i and therefore, this value is given 0.01 equal to L i into L i into L i. So, this is equal to L i cubed. Therefore, L i is equal to cube root of 0.01 right. Now, if I solve this this is equal to 0.21544. So, what we have said doing here is that the problem gives us the overall payload mass fraction and it also states that every stage all three stages have the same payload mass fraction. Now, if the payload mass fraction value is same for all the stages then from this equation we have just proved that this equation is valid for any multi stage rocket. We says that the product of individual stage payload mass fraction is equal to the overall payload mass fraction. So, we have used this equation here L is equal to i equal to 1 to n L i. This value is given we have from there we can calculate what is the payload mass fraction for individual stages. So, now this is equal to 0.21544. So, this is the first stage of the problem done. Now, let us come to the second part of the problem. With this now we have to estimate delta v delta v is our velocity increment. For that we go back to our expression for multi stage velocity increment. So, we have seen that delta v is equal to sigma i equal to 1 to n delta sorry delta u delta u i. This we have seen and this is equal to i equal to 1 to n u equivalent L n r i. We have also seen this u equivalent we can write it as i s p. So, we can get it as i s p i g e L n r i. Now in this problem what are the parameters given to us? After we have solved this what is given to us are epsilon 1 epsilon 2 epsilon 3 and sorry this is epsilon 3 and L 1 L 2 L 3. So, essentially this r is given in terms of L i and epsilon i. We had derived a relationship relating r and epsilon r i L and epsilon. So, now if I put it back here this is equal to sigma i equal to 1 to n i s p i g e L n 1 upon L i 1 minus epsilon i plus epsilon i. This is the relationship that we had derived. Now let us look at this equation. This is what we want to estimate what is given to us is i s p 1 i s p 2 i s p 3. So, these are given g e is known acceleration due to gravity at sea level is a known parameter epsilon i is given. So, that means epsilon 1 epsilon 2 epsilon 3 is given L i we need and we have estimated L 1 L 2 L 3. So, therefore, all the parameters in our right hand side are now known.  Now if I look at this the first term for i equal to 1 is this. For i equal to 2 this term remains same because our L i is same for all three stages and this term also remains same because epsilon i is same for all three stages. So, only thing that is going to change is i s p i. So, what I will do is the I will rewrite it as this term is same and here I will add the i s p values 300 plus 350. So, essentially what I am doing is I have this value as a constant and then to this I am multiplying sum of three i s p values two half two fifty three hundred and three fifty seconds. Now after this then if we solve this the delta v value comes out to be equal to 10 8 1 1 prime 0.37 meter per second. So, this is the value of delta v for this problem. So, now we know how to estimate delta v for given conditions. Later on in the next lecture what we are going to see is how do we optimize this that is we are given some parameters how do we distribute it so that we get this value maximum. So, we will be given some constraints under this constraints we would like to maximize the velocity increment that we can attend for this for the multistage rocket. This example I have given is a very simple example where all the structural coefficients were equal and the stage payload mass fractions were equal. But in reality you may not have the same condition here only thing that was differing was the i s p. In reality you may have different distribution depending on the mission requirement you may need to have different distribution. So, that we can optimize the performance of the rocket. So, far we have seen how a multistage rocket works we have considered this or free space because as I have said that the drag and gravity can be neglected for most practical applications. So, we work with this expression we have expressed r i in terms of different parameters. So, depending on what are the values given we choose for that is why I have taken this example. In this example what we have seen is that the certain values were given the L values were calculated. So, we use this form of the equation, but if let us say instead of this something else were given then we use a different form of the equation. So, therefore, there is a depending on the given parameters we choose which is the equation that needs to be used. And then essentially the governing equation is this we put it here and get the final expression for our velocity increment that is not going to change only thing is changes going to be that what form of r we are using. So, let us stop here today and in the next class we will take up the optimization of multistage rockets. Thank you.


Hi everyone, welcome to Online Voting Theory and Practice by Porter Adams and Emily Stam. We are at the DEFCON Crypto Village in August 2020. My name is Porter Adams. I am a software engineer at Blacktop Government Solutions and founder of Disappeared Digital. You can contact me at Twitter at Privacy Porter. I'm Emily. I'm a security research engineer at Allstate. I'm also the COO and co-founder of Cybersecurity Nonprofit or CSMP and you can find me on Instagram at Crypto.Emily. So I talk outline, we've got three major pieces, we're doing a quick intro now and then I will be talking about the practice of online voting and Emily will talk about the theory of online voting going into homomorphic encryption, mixed nets, and blind signatures. Scope of our talk, so we're talking about online voting, so not all election security, not even all voting, just online voting. So what do I mean by that? So one form of online voting is anything is called electronic voting or e-voting and that just refers to something that includes at least some electronics. So the United States, a lot of our voting systems already use e-voting by having computer screens that you can touch, but e-voting does not necessarily mean all online. Internet voting is what people would think of as like 100% online. Internet voting is when it's all gone fully digital and there's no need for in-person, anything in-person. So safety of voting machines, I'm just going to refer you to the DEF CON voting village. They do a lot of really great work over there. It's not the focus of our talk, we're going to be talking more about the internet voting side of things and how it would be possible to vote entirely online. So this is the biggest question I get is why can't we all vote from our phones? And it's a really great question and so we're going to spend some time explaining actual reasons why we can't yet. The advantage and why people want to vote from our phones in the first place, the first one is just the convenience factor. It's so much easier if I can sit at home and vote from my phone. It's also especially easier for overseas voters who if they currently have to vote by mail that can take a long time for their mail to get in and their votes may not even be counted by the time and so it's a lot easier for expats to vote from their phones. It also would hopefully improve voter turnout because it's a lot less effort to download an app on my phone and click some buttons than it is to show up at the polling station. That's human error. So we all remember the 2000 election with the hanging chads in Florida and not being able to determine which way the votes went. When we vote on a computer it's either a zero or one so it's pretty clear and doesn't leave room for human error when filling out the ballot. So let's talk a bit about usability. So even if we had a totally working mobile app that everyone like could download and use and was all safe and private which are concerns I'll get to later in the talk. In Finland in 2008 they had some issues with the user interface and what happened was people when they were going to vote they would see the screen they would tap through click all the candidates they wanted to vote for but at the bottom of the screen was a submit button and about 2 percent of voters did not see the submit button on the screen and therefore their votes were not counted and the Finland election 2008 is a user interface problem that would be a big issue if people tried to vote but mistakenly like didn't hit submit button that would be a concern even if everything else was safe and secure and working. The other case I want to bring up is Iowa in 2020 at the Democratic caucus had many problems with their mobile app that they tried to use to help tally up the votes we can learn a lot of lessons from that but one I want to highlight is that some people had trouble even downloading the app correctly and so even again if we had like all the security and privacy stuff worked out there's still some usability concerns with can people download the app can people use the app all of this kind of comes down to like comfort with electronics which a lot of us have here at like DEFCON but not everyone else in the world is as comfortable as we are with using these things. So here are some of the big concerns and security is by far the biggest one we need to make sure that our elections actually safe privacy is making sure like is it possible to even do a secret ballot online because we all know there's so much tracking and surveillance with what we do online that having actually private vote pretty tough so I'm going to try and answer both these questions and the remainder of my talk. So first security is it safe there is a huge attack service for anything that's going to be online some sort of mobile app and so let's just kind of go quickly over like all the different ways that would need to be like that could be a voting app could be attacked by and we would need if we wanted to do this in practice to sure up all of these things and make sure that none of these could happen. So if I was a hacker trying to attack a voting app I could install a back door either as you vote on the client side or when the votes are tallied on the server side I could create an exploit for the voting app itself or for the phone operating system or for the server code server operating system I could spy on votes by intercepting the connection maybe with a fake wireless access point or a key logger on person's device there's always social engineering you'd have to worry about with phishing app insider threat whoever like created the code for any of these pieces you have to watch out for and I was running the election and then just destructive attacks like a distributed denial service where the app just goes down on the day we're all supposed to be voting. OK, so usually when I'm trying to explain all this to someone they always come up with but banks have mobile apps and this is a really smart point and so it's worth addressing why even though banks have mobile apps it's still very tough for a voting system to be on a mobile app. So what's the difference between a voting app and a banking app? First one's identity when you're banking basically anyone with your credit card info can go online order some stuff on Amazon but when you're voting we need to make sure that is really only you. In terms of security banking has the benefit of being able to detect fraud kind of later and afterwards whereas with an election if there's any sort of fraud going on we need to know about it immediately and privacy is one of the biggest differences where when it's just you and your bank talking and like your bank knows everything and you know all of your own stuff that's fairly easy to figure out just between the two of you but for voting we all have secret ballots which I'll get to in a little bit it makes it very challenging for my vote to stay secret while everybody else still trusting that votes were placed correctly and then lastly trust in banking like it's really just between you and the bank and other accounts like don't really affect you or like other people using your bank versus in a voting system in a voting app I need to trust all of the votes from everybody not just my own and so trust is very different for a voting app so the privacy challenges specifically of online voting first you got the secret ballot and so what does that mean more or less that I need to be anonymous when I vote so no one should be able to figure out based on like like no one should be able to figure out who I voted for and there shouldn't even be a way for me to prove it to anyone next to each other next to me or around me so no one can force me to vote a certain way it's very important for our elections voter registration is not exactly a privacy challenge it's like an identity thing but it's going to be kind of related so I include it here voter registration it needs I need to be very sure that like whoever is submitting the information this voting app is the person on the registration list and this counts against like double voting which on the internet is much more it would be much easier to happen where you could submit something twice and have it accidentally be double counted and trust is the big third privacy challenge where all votes must be trusted and typically to ensure that trust that means lots of visibility and so the big the challenge here overall is combining the secret ballots with trust and you have to somehow like include all the anonymity expected for voters while still having all the visibility needed for the overall election and everyone to trust the results and putting these two together digitally is actually extremely tough and will require some really cool math that Emily will talk about in the second half of this talk so it's cryptography for online voting is the answer it's going to solve all of our privacy concerns and I just want to say big thanks to cryptographer David Chom for inventing a lot of this stuff I know if you're at the crypto privacy village at Defcon and have not heard of David Chom before please look up some of this work he's done awesome stuff okay so how does Estonia vote online especially in the United States anytime this gets brought up it's like how is some other country doing it but we can't first steps identity and Estonia they all have a national ID card that includes a chip on it where they can create digital signatures from which essentially means their like government issued IDs can act as a form of identity on the internet so they can log in using these chips although I believe in the last two years they have switched from hardware chips to an authenticator app but this still stands that they have some sort of way of converting from your real life presence to your online presence secondly cryptography Estonia uses a combination of I think mixnets and homomorphic encryption specifically using El Gamal and Emily will explain what those are in the later half of this talk and in terms of trust Estonia has been voting online since I think 2005 and every year they keep making gradual improvements anytime security people go check out there's always something that's broken which isn't really surprised but Estonia has done a good job of fixing the things that are broken and over time it's the system's gotten a lot better and hopefully is is mostly safe from real threats they haven't had any giant accusations of election interference so either that means they haven't caught anyone interfering in their elections or they've actually been doing a good job in 2019 almost a quarter million Estonian Estonians voted online which is very impressive numbers and goes to show that this is like possible in the future if it is done slowly and correctly now one big thing to watch out for is cryptographic backdoors these are tough to catch so Switzerland has been doing online voting and some researchers looked into their mix net shuffle proof and found a naive implementation of the zero knowledge proofs inside of there which would have allowed for all of the votes to be changed by an attacker and so making sure that like every last inch of the app needs to be like very carefully done and especially when it comes to cryptography you need the person who's coding it to be aware of all of the cryptographic assumptions and make sure that they are coding in everything properly so let's look at voting cryptography around the world three big ones I want to point out are in Estonia Switzerland and then Moscow has some local elections that are online and Estonia uses a combination of homomorphic encryption and mix nets same thing for Switzerland and Moscow is using homomorphic encryption and blind signatures so not too many like countries of places around the world have an online option right now there are a lot more countries that have tried doing this and quit Belgium Finland France Germany Ireland Kazakhstan Netherlands Norway are on the list and the reasons for for quitting are mostly either every security person says it's not very safe or the voter trust in an online system is just not very high and one of the most important things for an election is that voters do trust the system and so even if online voting is safe if the voters all think that it's not safe then it's not a good idea to offer an internet voting option all right so now I'll talk about the cryptography behind the scheme all right so now talk about the cryptography behind the scenes that makes online voting possible so some of the considerations we have the first is security so preventing attacks preventing adversaries from tampering with the election and being able to detect faulty voters and centers second is robustness so no small set of servers should be able to disrupt the election accuracy the result should reflect the way people actually voted verify ability we should be able to verify that the votes are accurate in particular individuals should be able to verify that their vote was counted correctly confidentiality keeping votes secret is crucial usability for all ages and speed and efficiency including casting the votes processing them and counting them so there are three types of cryptographic protocols I'll cover in this talk homomorphic encryption mixed networks and blind signatures so first homomorphic encryption so homomorphic encryption is computation on encrypted data so this form of encryption actually allows us to do computations on the data when it's in its encrypted state there's been a lot of research into this area and it's very promising because generally our cryptography when we have our data and it's encrypted we can't use that data in any way the only way we can actually make use of it is to decrypt it back into its original form but with homomorphic encryption we can actually perform computations on the encrypted data so this means we could outsource data to cloud environments for processing all while encrypted we could perform data analysis again while data remains in its encrypted form and in particular with election voting we could obtain a tally of the encrypted votes without actually having to decrypt the individual votes maintaining privacy the entire time so to give a little bit more of the mathematics of the scheme so homomorphic the term actually comes from a math term called homomorphism which is a math that preserves some structure so that's what you can kind of think of homomorphic encryption as doing it preserves some underlying structure enough to perform functions on it so you have a message you encrypt that message you perform a function on it and then you decrypt it and that would be the same thing as if you apply the function directly to the message and there's different types of homomorphic encryption generally they are categorized based on what kinds of computations you can perform whether it's just partial whether it's addition multiplication but we even have fully homomorphic encryption and that actually can perform arbitrary gates and depth meaning really arbitrary computations the only practical and secure fully homomorphic encryption implementations currently are based off of lattices so lattice cryptography it's this new relatively new form of cryptography that is beginning a lot of attention recently partially because it's quantum secure cryptography meaning that it's secure against quantum computers and it's actually most of the finalists and the post quantum cryptography NIST competition are lattice based and lattice cryptography has some very strong security assumptions especially compared to our classical cryptography like RSA it's also very flexible and efficient generally the main downside is that it has large key sizes but depending on the scheme they're not even always that much larger than RSA so lattice cryptography is very important for the fully homomorphic encryption but we'll also touch on it when we come back to blind signatures so I just wanted to mention what that is and so now we'll turn back to homomorphic encryption and voting in particular so how does it help so we can tally the votes in the encrypted state which means we take all the votes in in their encrypted state add them together and then decrypt the result and because of the homomorphic encryption we get the same result as if we decrypted them separately and added them together so this allows voters to maintain their privacy there's also a protocol that allows us to allows voters to verify their votes and even if we don't use homomorphic encryption in the election we can still use it for ballot comparison so ballot comparison is very important in the election process to inspire voter confidence by comparing ballots and the electronic records and the way we can use homomorphic encryption is this in this is that we can actually do this comparison on the votes in their encrypted state so we would inspire voter confidence without actually giving any information about the votes and how this done now is the votes are anonymous but even still with anonymous but not tying them back to the individuals you can still find patterns so it would be more secure if they were in their encrypted state so next I'll talk about mixed networks so mixed networks also called mixed nets are routing protocols that use a chain of proxy servers mixes to take in messages from senders and send them to receivers in some random order additionally they use encryption at each state and it makes it harder to trace and you can also think of it as being kind of like a Russian doll some nested encryption going through so there's two types there's the decryption mix net so that's where you do all the encryption in the beginning and then you partially decrypt and mix at each stage there's also re-encryption where you re-encrypt and mix at each stage and do do the full decryption at the last round and there's also shuffle and decrypt proofs for verifications as well so lastly we'll talk about blind signatures so just to recall a digital signature provides authenticity so verifying that you're talking to the person you think you are verifying a known sender and integrity verifying that the message you're receiving has not been altered in transit maliciously or accidentally so how it works is one party signs the message and creates a signature with a private key and then the other party will verify that with a public key so with blind signatures it's a digital signature where the message is masked or blinded and then sent and then signed so blind signatures can then be verified against the original message the same way digital signatures are the key difference is that with blind signatures the person signing them doesn't know the contents of the message so voting is actually a common analogy with blind signatures so imagine you have a voter and they complete an anonymous ballot which they then place in an envelope with their credentials they hand that envelope to an official who signs it and the signature of the official imprints through the envelope onto the ballot and they return that envelope to the voter the voter then places the ballot in a different unmarked envelope before submitting it so now the message was correctly and sufficiently signed by an official without the official having to know the contents of the message so it provided the authenticity and integrity but maintain the confidentiality so to talk a little bit more about the scheme in a less analogous way what actually happens so a user has some message D and they blind the message to get a new message D star and that's what they send to the signer the signer then uses the private key to generate a signature Sigma star for that message D star and returns it to the user the user can then create from Sigma star a valid signature Sigma corresponding to their original message so any recipient can now validate this signature Sigma as they would any other signature and the signer gets no information about the contents of the message or the actual signature and there's different mathematics behind blind signatures there are RSA based options I don't I wouldn't recommend using these because with where we are right now if we're implementing new technology we want to be looking as far ahead as possible and in the long run RSA is not secure against quantum computers and just as not secure compared to these other types of schemes but there's also some attacks on the RSA based blind signatures so I am mostly gonna focus on the lattice and the multivariate base so the lattice based blind signatures again they're post-quantum secure and they rely on similar problems similar types of schemes as those that are finalists in the NIST post-quantum cryptography competition so we have a lot of faith in these lattice based schemes and we can create blind signatures from them additionally multivariate there's a scheme called the rainbow scheme that's a finalist in the NIST post-quantum cryptography signature schemes competition so again leads to be post-quantum secure and we can turn this scheme into a blind signature scheme and there's a lot of benefits to multivariate cryptography such as having very fast and short signatures and this diagram just kind of shows how the rainbow scheme works essentially you have a message W the hashed message and you recursively obtain inverses of these functions to get the signature Z and then that signature Z can be verified by using the public key function and just applying that to see if you get the correct message back with blind signatures there's just an extra some extra steps in this process you use a special function called R that actually by using that you create the blind aspect of it and then you use use zero knowledge proofs at the end as well as part of the verification proof so a little bit more complicated but again very similar mathematics so in summary we talked about homomorphic encryption so computation on encrypted votes which allows us to tally the votes in their encrypted form and it can use different types of cryptography but lattice base is one that is post-quantum secure and very flexible then we talked about the mixed networks protocol where you have a nested series of encryption or re-encryptions and shufflings and this way you cannot determine which person the vote came from and there's also a range of underlying public key cryptography mathematics that I didn't go over but the protocol itself is fairly flexible and finally we talked about blind signatures so this is where you create a valid signature without knowing the contents of the message so you're verifying authenticity and integrity of a vote while maintaining confidentiality of a voter and we talked about lattice and multivariate based schemes to summarize everything is it possible theoretically yes eventually cryptographers will help us get it right as long as security people is it ready in practice not yet in the United States let's start small scale and maybe eventually we'll be able to have more voters vote from their phones so thank you thank you for coming to the talk