What we've covered in the course so far, we started with encryption, that is the concepts of encryption and one of the main uses for encryption is for confidentiality, that is I have a message, I want to send that message to someone else and I want to make sure that no one in between can read my message. I want to keep my message private or confidential. We started with symmetric key encryption. So we went through the classical ciphers and some of the real ciphers, symmetric key encryption and remember that both the source and the destination must have the same shared secret key. So it's called symmetric key encryption, sometimes it's called secret key encryption or shared key encryption or even there's some other names as well. But the one where we have a same key at both source and destination, one key. And then we went and introduced public key cryptography where we have two different keys. They are related though, the keys are generated and related and we can use them in opposite order in some cases where we encrypt with a public key and decrypt with a private key or the other way around, decrypt, encrypt with a private key to sign a message and to verify decrypt with a public key. And that's when we move on to authentication and we spoke about hash functions can be used in authenticating messages and also there are other ways to authenticate messages. We can authenticate messages using normal encryption because if it successfully decrypts with symmetric key encryption then it's an indicator that it was encrypted with the right key and by the same person who has that key. And we saw the last topic very quickly last week was on message authentication codes, an alternative for getting some short representation of the message that we use for authentication. So hash functions, message authentication codes used for the same purpose authentication. And that this next topic after we go through this next topic covers the main operations that we use in cryptography. There are some others but these are the main ones so encryption in the different forms and authentication that are the main operations we have available. This topic is about how do we distribute keys? How do we make sure that the correct users have the correct keys? So it's a problem that we've mentioned throughout the other topics. For example with shared secret key encryption somehow I need to get the key to the other person. That's a problem and public key cryptography is a way to overcome that problem but public key cryptography has its own limitations in key distribution as well. So now we're going to talk about if we have keys, secret keys or public private key pairs like you did in the assignment, you generate your own key pair, how do we get them to the other person or the other entities and how do we do it in a secure manner? That's managing keys and distributing keys. And we'll go through some general concepts with key distribution and some issues and then we'll go through some different cases. One, as you see it's not so clear here but we'll see that we'll look at if we've got symmetric key encryption, two users need the same shared secret key. I want to communicate with you with symmetric key encryption. We both need the same secret key. What's one way for those two users to securely exchange a key? What's the name of one algorithm that allows two users to securely exchange a secret? Diffie Hellman, you just did it in your assignment. In your assignment, you exchanged a secret between two users. You were one user and then I created this other user, your friend. And using Diffie Hellman, you exchanged some public values. So you generate your own key pair, exchange the public values and then derived the secret. And the secret that you derived should be the same value as the secret that the other user derived. That's how Diffie Hellman key exchange is used. That's one way to exchange a secret. There are others. So we'll go through different ways to exchange secret keys using both symmetric encryption and asymmetric encryption. And then we'll talk about how to exchange public keys. We've set up until now with public key encryption the advantage is I generate my own key pair, private and public, and then I tell everyone my public key. The concept sounds simple. The problem is how do you know it's my public key when I tell you? Someone could pretend to be me and publish Steve's public key, put it on a website and say this is Steve's public key, but in fact it's someone else's public key. So we also have problems with how to distribute public keys. So let's get started. First some general issues or some assumptions that we're going to make. Symmetric key encryption fast, it's good for encrypting a large amount of data. You have a file, you want to encrypt all the data you send across a connection. When you're downloading a file or using a secure shell for a terminal, then symmetric key encryption is normally used for that because it's fast. It can be implemented and run quickly when we have a large amount of data. It requires a shared secret key. The alternative asymmetric or public key cryptography doesn't work so well or is very inefficient when we want to encrypt a large amount of data. Therefore it's not very often is it used to encrypt a large amount of data. It can be, but it's slow. Therefore public key cryptography is mainly used for authentication, whereas symmetric key cryptography mainly used for encrypting data and often we combine them. We use symmetric key encryption to encrypt the data and public key encryption to provide authentication. The issues that arise that we need to cover is how do we share a symmetric key, a secret key, how do we get one from one user to another and then how do we distribute public keys. First, consider the case where we want to distribute or share secret keys and we're going to use symmetric key encryption to do so. So I cannot just send you a key by email. If I generate a key, I cannot send it to you. If I want to communicate across a network, across the internet, if I cannot write it down or send it in post, if I need to send across an electronic network, then I would need to encrypt that key, okay. And then the question is what key do I use to encrypt the key that I'm going to send you? Well in this case we're going to cover, we want to share a secret key using symmetric, a secret key to be used for symmetric key encryption and to share that key we're going to encrypt it using symmetric key encryption. So the issues or how do we do that, what's our aim, two entities share the same secret key, that's what we want to achieve. Now one of the principles that we'll introduce in this topic is that we don't want to use one shared secret key forever, okay. That is two users exchange a secret key, we communicate for a day using that key, encrypting our data with that key. For security reasons it makes sense to change that key on a regular basis. Do not use that same key for the next three years. Why? Because the more times you use that key, the more opportunity the attacker has for trying to discover that key. Either using a brute force attack or using some other analytical attack. Or just trying to find your key via other methods of seeing what you've written down on a piece of paper and so on. So a general principle is that you don't want to use a key for too long.  Given that, how do we exchange a secret key? Different options and some of them are related. Four options listed here. First one, A, physically delivers a key to B, okay. I want to communicate with one other user. I write my key, I select a key, I write it down on a piece of paper, and I give it to that other user, not via the network. So I physically give them the piece of paper or somehow deliver the key to them physically. So we do not send the key across the network, okay, in that case. If I physically deliver it. Possible, very inconvenient. It's okay if I want to do it to communicate with a group of students. We could do that. But if I want to communicate with people on the other side of the world across the internet, it's not very convenient. And especially if I want to communicate with people now, right now, rather than having to wait a week to send by a post, then physical delivery of keys is not very convenient. It's time-consuming and it consumes a lot of effort. But it's possible. An alternative of that is that A and B want to share a secret key. They both need the same secret key. An alternative is to involve a third party, some other user, C. And get them to deliver the key. So for example, in our class, let's say all the students want to communicate securely. So one student, A, needs to exchange a secret key with another student, B. Rather than going direct to the other student, what you could do is that one student comes to me, the third party, C, and I give them a shared secret key. And when the other student wants to communicate with that one, they come to me as well, and I tell them the key that I gave the other person. So I, the third party, distribute the keys to the end users, those that want to communicate. That can be more convenient in some cases, say, in an organisation to have some third party, some central entity, to manage the keys and to distribute them. Still involves physical delivery, though. It's done not over the network, but via some other means. Then the next two, options three and four, related, in fact, depend upon the previous ones. If A and B already have a key that they've shared, then they can create a new key, encrypt that with the old key, the one they already have, and send it securely across the network. So in that case, if the two users have already shared a key, then quite simply, one user generates a new key, encrypts it using AES, triple depth, whatever, encrypts it using the old key and sends it across the network. And even if someone intercepts that on the network, they will not be able to see the new key because they don't have the old key, okay? So that's one approach, encrypt the key when we send it across the network. For that to work, A and B must already have a key. How do they get that? How do they get the key to start with? Anyone? Use one or two, okay? So in fact, this one, option three, and you'll see option four as well, depends upon one or two taking place in the past. So the option then is two users physically deliver a key. So both A and B have a key using option one. And then now A and B already have a key. So later when they want to use a new key, remember our principle, change keys frequently, when we want to have a new key, then they can use the old key and encrypt that and send it across the network encrypted. And number four is similar, except we involve a third party. That is, let's say A and C have a shared secret key already. B and C have a shared secret key already. Then when A wants to communicate with B, then C, this third party, can generate keys and send the same key to both A and B securely across a network. Again, it involves some physical delivery before we can get started. Let's compare them briefly. We'll see some of them take place in the later slides. Of course, option one and two, manual delivery or physical delivery, it's not very convenient. It's only really possible if there are only a few entities involved. So physical delivery may be, for example, the administrator of the network going around to every computer and programming in a key, typing in a key. So let's say in SIT, if we want to use encryption to communicate between all our PCs and laptops, then when you register your network, you have to go to the computer center and they type in the key to be used. So that's another form of manual delivery that is some human involvement in that. It only works when we have a small number of users or entities involved. Because as the number of users it grows, it takes much more effort to distribute those keys. And also across a small scale, that is it doesn't work across the globe. You cannot physically go to every computer, only say inside an organization it's convenient. So manual delivery in option one or two, option three or four require some initial distribution of keys. In option three, it requires the two users to distribute keys. And in option four, involves the users to have a key shared with user C and C distributes the keys. There are some issues that arise in that in option three, for example, when we encrypt our new key using the old key. Well, if someone discovers the old key, then they can find the new key. That's a potential problem in that case. The discovery of the initial key means that the attacker can also discover the subsequent keys. So we need to be careful how we use that. Using a third party is practical when we have large networks. For example, a large organization, because it's easier to have that entity distribute the keys than to have all the end users contact each other. We'll see some examples or some simple calculations in that shortly. So some general ways for how to distribute keys. We'll go through some of them in more detail. Let's say we're going to do manual delivery. And we have a network. Then one of the questions that arises is where do we perform the encryption if we want to securely communicate across that network? We'll describe these two. We'll use this example network to describe them. So this is a picture of a network where we have 10 hosts, the squares, A through to J, 10 computers in this network, small network inside SIT, for example, and some switches connected together and some routers. So small network, not very realistic, but we'll use it for our example. So we want to communicate between the hosts in a secure manner. That is, when A wants to communicate with J, for example, there's an application on computer A, wants to send some data to the application on computer J, we want to make sure that that data is encrypted so that if someone comes into our network and listens, tries to intercept the packets sent across this link, even though they can intercept the packets, they shouldn't be able to obtain the data. That's our goal. For example, here's our network. Let's say these links from CDE to the switch are actually wireless links using wireless LAN. They're not cables, but a wireless link. So CD and E are laptops and the switch is some wireless access point. Therefore, when E sends some data to someone else, they send it across a wireless link to the access point, the switch here. Same as my laptop sending wirelessly to an access point. It's very easy for someone to be sitting outside and to intercept and receive whatever I send. Whatever E sends across the wireless link, it's very easy to intercept all of those messages. Similar with a wired link, it's a bit harder to intercept, but it's possible. The difference with a wired link is that you need to be physically nearby to intercept. So let's say the wired link from this PC that goes into the socket on the wall and goes to a switch downstairs. Let's downstairs, it's upstairs. No, it's same floor, two rooms down in the computer center. So it just goes down there. How do you intercept what I send from this PC? If this is PCJ, how do you intercept it? What are you gonna do?  What do you need to do to intercept the packets that I send? It's across a wired link. Cut the wire, okay? All right, yes, basically. Let's say you've got your own laptop. You sneak into this building or a nearby building and one option is this blue wire here, this LAN cable. If normally we send our packets across here, if you can put a device, cut the wire and put a device in the middle that takes a copy of everything that's sent across there and sends it to your laptop, then you've intercepted everything that this computer sends. So it's possible, except you need physical access to this network to do so. Whereas with wireless LAN, it's a bit easier because with wireless LAN, I send to the access point, but my signal goes everywhere. You can sit outside, possibly even downstairs in the cafeteria and intercept my messages. We want to stop that. Here's our network. Assume an attacker can intercept along any link. How do we stop them from accessing our data? That's the question. Well, we use encryption. We encrypt our data. When he sends data, it encrypts it. So that even if someone intercepts across the link, they cannot see the contents of the data. Now the question is that we're trying to, we're going to address here is where do we encrypt? What are the options for, at what locations in the network do we encrypt? First option we'll consider is, let's go, let's say end-to-end encryption, called end-to-end encryption. First option, let's say every computer encrypts the data, every host. For example, when E wants to send to J, E takes the message that they want to send to J. They encrypt it using AES, RC4, whatever they choose, assuming they've distributed keys. We'll come back to that in a moment. They encrypt it, they send it across this link to the switch. The switch does its normal job of sends it to the router to switch for, router for, switch six, and it arrives at J and J decrypts. This is what we call end-to-end encryption in that it's the end hosts, the two points that are communicating that are doing the encryption and decryption. So that's one option. Another option is that have encryption being performed across every link. So, E wants to send some data to J. What happens is that the LAN card on E, when it has that data, it encrypts the data and it encrypts it with a key which is shared with switch two. Encrypts the data, sends it across the link to the switch. Then the switch decrypts the data, gets the original data back, the plain text, and then the switch encrypts it again to send across the next link to router one. And then the router one decrypts and then encrypts again to send across the next link. And we keep going until switch six receives the data, encrypts and sends across the link to J, J, the LAN card decrypts and gets the original data. That's link level encryption. We encrypt on each individual link. Which one do we use? Well, what are the advantages and disadvantages of each? Both of them provide our security from our attacker that tries to intercept on a link. Some attacker listens on this link. In both of those cases, whatever is sent across the link will be encrypted. So the attacker will not be able to get the message. With end to end encryption, E encrypts, J decrypts, across this link between switch two and router one, whatever is sent across there is encrypted. Contents cannot be seen. Same with link level encryption. Switch two encrypts, sends to router one, and if someone intercepts, again, the message is encrypted, they cannot see the plain text. So that objective of securing the data is achieved. How many keys do we need if we use link level encryption in this case? So with link level encryption, each endpoint of each link must exchange a secret key. E to send to switch two. Both E and switch two must have one shared secret key. How many keys are needed in the network? Not just for the path from E to J, but assume anyone else wants to communicate as well. So how many keys are needed if we use link level encryption? Someone's got 20, I can't remember the answer. Anyone? Where do you get 20 from? The number of links, okay? You count the number of links. And if you count, I can't remember, how many, one, two, three, four, five, you count all the links and 20 links there. For every link, each endpoint of that link has a shared secret key. So E shares a key with switch two. D shares another key with switch two, a different key. And C with switch two, and also switch two with router R1. So there are four keys shared there. Let's record how many we have with link level encryption. In our example network, we need 20 keys. What if we want to use as an alternative end-to-end encryption between hosts? How many keys do we need? That is, E wants to be able to communicate with J or any of the others. And similar with the other hosts. How many keys do we need? Count them or calculate. Anyone have an answer? But for end-to-end encryption between the hosts, we'll come to another special case later between applications, but between hosts. End-to-end, between hosts. How many keys would we need if we use this approach? Someone's got 25, I don't think it's enough. It's a few more than 25, but not many. How do you calculate it? I don't want you to count them all. You could, but what do you consider? Consider there are 10 hosts here. A through to J, there are 10 computers. So how many keys does A need to share with other hosts? A with B, A with C, A with D, up to A with J. So there's nine keys there. What about B with others? B needs to share nine keys with others. But in fact, one of those keys is shared with A, so we just count eight keys. And C, there's a key shared with A, there's a key shared with B plus seven others. And then add them up for the rest. And what's the answer? Not factorial, 45 in this case. You add them up. Nine plus eight plus seven. And to make your life easier, sometimes it's nice to remember a general formula. If we have, it's the number of pairs between these 10 devices. So let's say if we had just A, B and C, how many pairs will A to B and C, C to B? We have three in this case. If we have four devices, we have six pairs. And there's a general formula for that. How many pairs between N entities? And it's N by N minus one over two, where N is the number of entities. For example, 10, 10 by nine, which is 90 divided by two is 45 in this case. So if we used end-to-end encryption for this network, we'd need to share 45 keys. If we increase the number of hosts in this network from 10 up to 20, if we had 20 hosts, we'd need, what is it? About 200 keys. 190 keys, I think. 20 times 19 is 380 divided by two is 190. If we had 20 hosts in the network, let's say more hosts attached to this switch two, another 10 hosts attached to switch two, with end-to-end encryption, we'd need to share 190 keys. But with link-level encryption, if we attached another 10 hosts here, we'd need just 30 keys, another 10, because there'd be another 10 links to this switch. So in general, with link-level encryption, the number of keys that we need to exchange is much less than if we use host or end-to-end encryption. And that's the advantage or an advantage of link-level encryption. If we want to manually set up the network and manually program in keys, it's possible in this network with link-level encryption. What we do is for each computer, when the network admin, they set up the computers here, they program in a key. And same with a switch, there's a key programmed in for each link. That's possible for a small network. But to allow any host to communicate with any host, okay, with 10 hosts, 45 keys possible, increase it to 20 hosts, 190 keys, it means you need to program in 190 keys throughout that network. So as you increase your network to 1,000 hosts, then you need something like 500,000 keys to program in. So the number of keys grows rapidly in that case. So in link-level encryption, manual delivery of keys may be possible for small networks. End-to-end encryption, not so feasible. What's the advantage of end-to-end encryption then? Link-level encryption has this advantage of you don't need so many keys to be distributed. Why would we use end-to-end encryption? Why do you think you'd use end-to-end encryption in this case, instead of link-level encryption? Advantage of link-level, less keys, that's a good thing, but there's a bad thing. Anyone? Think about what the steps are to send from E through to J. With link-level encryption, take your data at E, encrypt, send it across the link, decrypt at the switch, get the original plain text, encrypt it again, and send the ciphertext across the next link, and do that at each device, correct? Two things. At each device, we need to encrypt and decrypt a performance issue, that is at the switch, we need to decrypt and then encrypt again. That takes time. And then at this router, we decrypt what we receive and then encrypt again with a different key to send across the next link, so performance is an issue. With end-to-end encryption, we encrypt at E only, and only decrypt at J. What else, so performance? Security, because in general, it's more secure using end-to-end encryption because we decrypt at the switch. So in memory at the switch, it receives a packet, the ciphertext, it decrypts, it has the plain text in memory, and then encrypts that plain text again and sends the ciphertext. So at some point inside the switch, the plain text is visible. So if an attacker can get physical access to the switch, they can potentially see the data, similar with each of the other devices in the network. If the attacker can get physical access to the devices, they can see the contents of your plain text. So that's the bad thing about link-level encryption. If we can secure the devices, then it can be a possible approach. For example, it's not very easy for you to get access to the switches in SIT because you need to go into the computer center and they have a door lock on that, okay? So they have another form of security. But if you don't trust the people who run the computer center in that they may want to intercept something that you're sending to someone else, then link-level encryption is not suitable in this case. Now consider communications across the internet. That is, this is a much larger network. And to end encryption, we have many more hosts. We need many more keys. That's a bad thing. But link-level encryption, if I want to communicate between my laptop and some server securely, I must trust that all the internet service providers between my laptop and the server are using link-level encryption and that no one is accessing their switches and routers and so on. I don't trust anyone in the internet to do that. So it's not suitable for a large network, link-level encryption. It's only suitable for small networks when, for example, one organization runs all the links. So summarize that. Link-level encryption encrypt across individual links. Each link endpoint shares a secret. The intermediate devices must decrypt and encrypt. That's some performance penalty. That's bad for performance. And for security, we must make sure that all links and devices support encryption. If this link didn't encrypt, then my data from E to J, I would not consider secure. Even if these links encrypt, if one of them doesn't, then all the attacker has to do is intercept on that link and they get my data. So we must have all links support encryption. With end-to-end encryption, the endpoints, the hosts encrypt the data. Now, the endpoints may be either the computer, the host itself, or in some cases the application on that computer. My computer runs multiple networked applications. A web browser and an email client. Rather than my computer encrypting all data, the web browser encrypts data and sends it to a web server. Separately, my email client encrypts data and sends it to an email server. So that's at the application level. Each pair of hosts or applications must share a secret key and hence there are many more keys needed. But the advantage is that it doesn't rely on intermediate devices for security. We don't have to trust everyone inside the network. You just need to trust the endpoints. And that's what's generally used in the internet for secure communications. What if I have on all of those 10 computers three different applications running? Three different networked applications. For example, one of the applications on E may want to communicate with its corresponding application on J. But at the same time, another application on E may be communicating with a corresponding application on I and someone else. So let's say there are three separate applications on each of those 10 computers. How many keys do we need? When we just had host to host, we needed a 45 keys. What if we have security or encryption between applications? How many keys do we need? Assuming three apps per host. Anyone with an answer? In fact, I'll accept two different answers. It depends on different conditions. Anyone calculate the simple answer? Three applications per host. We said with host to host, we had 45 keys. Three applications per host. Let's consider E and J, for example. There are three applications on each of those computers. Well, it depends on our assumption. If we assume that this application A, these are the applications, A will only want to communicate with A on this computer. A will, the application A will not want to communicate with the application B or C on this computer. So A with A, B with B and C with C. If that's the case, for example, A is a web browser, here it's a web server. This is an email client, email server, instant messaging, instant messaging. Then it's just three times 45. The number of keys would be three times 45. Is it 35? If we allowed A to communicate with application A, B or C on another computer, and also on all the other computers, what's the answer? If any application could communicate with any other application, then each pair must share a separate secret key. So how many keys do we need? How many entities do we have communicating? Maybe not the final answer, how would you calculate it? Again, three times 10 use that formula, correct. Effectively, we have three applications on each of the 10 computers. We have 30 entities that need to communicate. There are 30 different applications in the network. Each can communicate with any other. So one communicates with 29 others and so on. Using this formula, N equals 30. 30 times 29, it's about 450. 30 by 30 is 900 divided by two is 450, it's less than 450. So in this case, 450 keys or up to 450 keys are needed. And in many networks, we want to communicate securely between applications. Even in this small network, if we want to allow that, with just three applications, hundreds of keys are needed, depending upon the assumption, 135, 450. The point is with end-to-end encryption, we cannot rely on manual delivery of these keys. We cannot rely on someone passing around a piece of paper or going to every computer and programming in each key. We need some way to automatically deliver those keys because there are too many of them. So we need some automatic key distribution. And one approach is to use a key distribution center, some other device in the network that all of the entities trust. So we say a trusted third party, some other entity. Everyone else trusts them and they assist in distributing the keys. And we have different types of keys. And this is common terminology for different systems. We have our data that we send between entities. So the data sent between E and J is encrypted using a session key. To get this session key, the KDC distributes it to E and J. So although it's not on the diagram, let's say there's some other computer here, a key distribution center, a KDC. So what happens is that KDC distributes session keys to each entity that wants to communicate automatically across the network, not manually. And for the KDC to send a session key to E, it must be encrypted. And it's encrypted using a master key. So each host or application shares a master key with the KDC. And when we want to use a session key, we encrypt it using the master key and send it to the entity, E, J, one of those hosts. And then they use the session key to encrypt their data. So we have two levels of keys, master and session keys. In our network, let's say there's a KDC, a special server attached to router one. How many master keys do we need? How many master keys? Where the master keys are used to communicate securely between a host and the KDC. If A wants to get a session key from the KDC, they use the master key to encrypt that session key. So how many master keys would be needed in this example? What was that? Five, no. 45, no. 10. 10 master keys. Why 10? One shared between the KDC and A. Now I'm assuming between hosts here, not between applications. One between KDC and B and so on and KDC and J. One for each host or entity that wants to communicate. And then what happens using some protocol and we'll see an example soon when E wants to communicate with J, what happens is they go to the KDC and say I want to communicate with J. And the KDC creates a session key. Creates a session key to be used between E and J. And the KDC encrypts that session key using the master key shared with E, sends the session key across the network to E. And similar, encrypts the same session key using the master key shared with J and sends that to J. So that both E and J receive this session key across the network, it's been encrypted. So whoever intercepted any messages will not be able to see the session key. It was encrypted with the corresponding master key. So the distribution of the session keys is automatic. It's done over the network. Whereas the master keys are normally distributed manually. That is, we program into the 10 computers the master key. With manual delivery, we can do it when there's just a few number of entities involved, when there's a few keys. With session keys, it's better to automatically distribute them because there may be many session keys. In our case, we need, in our simple case, we need 45 potential session keys. And we have 10 master keys. Master keys would be manually delivered, whereas the session keys would be automatically delivered across the network. And the session keys are encrypted using the master key. So we've increased the total number of keys to 10 plus 45 session keys, 55 keys in total. But importantly, only the 10 master keys need to be manually delivered. And all of the session keys can be encrypted and sent across the network. Master keys can be distributed manually. Session keys are encrypted with the master key. And our data is encrypted with a session key. That's the idea of a KDC. We can look at this hierarchy of keys in this diagram. That is, when we have data, we want to send it across the network. We encrypt it with a session key, which provides cryptographic protection of that data. If anyone intercepts the message, they cannot see the contents because it's encrypted. Similar, whenever we want to send a session key across the network, we encrypt it with a master key. And therefore, anyone who intercepts that packet, that message, will not be able to see the contents, the session key. It's protected.  They are not sent across the network. They must be delivered in some other, using some other mechanism, some manual delivery. For example, the user goes to the KDC and they type in the master key.  So the master keys are delivered not across the network, but via some other secure channel. And this hierarchy makes it possible to use end-to-end encryption in a network. Although we may need thousands or millions of session keys, they are all distributed automatically across the network using some protocol. It's just the master keys which are delivered with manual delivery. Here's an example of a protocol that delivers keys between a KDC and the two users. Let's go through it. Let's get started now and after the break, we'll do some analysis of possible attacks. We have three entities. A wants to communicate with B. So computer A wants to send some data to B securely across some network. They could be anywhere in the network. They could be inside SIT's network or in the internet. So A is going to initiate some data communications to B, who's the responder. And there's this other entity, the KDC. And the KDC is trusted by A and B. And before anything happens, their assumption in this case is that there is a master key shared between the KDC and A and another master key shared between the KDC and B. Let's record them. And the notation used in this diagram, the master key is K, A and KB. They're the two master keys. Which means, and they were exchanged before this. They were exchanged manually somehow. That is, user A went to the KDC, the KDC selected a master key, stored it and told user A. And did the same thing with user B. Different keys. A only knows its master key. No one else's. The goal is for A and B to get a session key. So what we want is a session key, and in this case called KS, shared between A and B. So when A sends data to B, they will encrypt that data with a session key. So this is a protocol that assumes the master keys have been distributed and the goal is to distribute the session key between A and B. And there are five steps involved. In fact, the steps of distributing the key are the first three, step one, two and three. The last two are just for some extra authentication. Let's go through the steps and as we go introduce some of the notation. The first thing is that, so this is done over the network. So send some special packet. A sends a message to KDC saying, I want to communicate with B. Please generate a session key for me. That's the idea of message one. Saying I'm user A, I want to communicate with user B. Can you please create a session key and send it to me? Now the notation given here or what information is needed in that message, we need something about the identity of user A, IDA, that's who's making this request. The identity of the other user that we want to communicate with, IDB. N1 is what's called a nonce value. These are described on the next slide as well, a nonce value. The idea, we'll see the use for the nonce as we look at attacks, but one idea is one use is to prevent replay attacks so that we can identify this request. If it's replayed later, we'll be able to distinguish if it's the same as a replayed one or not. So we can sometimes think of as some unique identifier for the message or for the request. Often it could be a random number, maybe a time stamp. So some value that should be different each time we make a request. So if A sends a request to the KDC, five minutes later they send another request, they should have a different nonce value. If they use random numbers, long random numbers, they just generate a new nonce and of course it should be different similar with a time stamp, that something records the time, the down to seconds or milliseconds. So a nonce value, we'll see that come up in other protocols as well. But let's say just a random number for this example. Send it to the KDC. When the KDC receives this, they recognize this is a new request. It's not one of the old ones, it's not a replay of the old request because they see it's a new nonce value coming from user A. And what they do is that they generate a session key, KS. And then they send back this response. So in this protocol, the KDC chooses the session key that A and B are gonna use. So at the end of this, A will know KS, B will know KS, and KDC will also know KS. That's acceptable because we trust the KDC. So the assumption here is that A and B don't care if the KDC can see the contents of the messages, they trust the KDC. So the KDC generates KS and sends that back in a response. And the response really has two parts. The first part, and we see the E here is we apply encryption, some cipher using some key. So the first parameter of the encryption is the key used and then the second is the plain text. So the first part here, and I'll write it on the board to make it a bit bigger, we encrypt using the master key of A, all of the data inside square brackets, KS, IDA, IDB, and the nonce. That's the first part of that message, message two. This is the plain text and it's encrypted with the master key key, key KA. What is the plain text? The plain text is the requested data, IDA, IDB, nonce, and one, same values as what was sent in step one, as well as the session key, the key that A and B are going to use. Encrypted with a master key, KA means only user A can decrypt because only A has K, A. A and KDC, the KDC sent this message. So when A receives message two, it decrypts using its master key and when it decrypts, it checks the values. Do these values, IDA, IDB, N1, match what I sent in message one? To just check that this is the correct response for the message that I sent. And also it learns the session key, KS. So after step two, user A knows the session key. User B doesn't yet. User B doesn't know anything's happened. Message two comes in two parts. We see a concatenation here, the second part. The second part I'll draw underneath is encrypt with KB, KS and IDA. That's the second part of message two. Can user A see the contents? User A cannot see the contents of this part. It's encrypted with the master key of B. So even though it's sent to A, message two, this last part here, user A cannot read the contents of that message. It's encrypted to using the master key of B. What's inside we'll see is the session key and the identity of A. But A cannot see that. All A does is takes that ciphertext, because this is ciphertext, and sends it as is in message three. They send it to B. So you see message three is just the end part of message two, this part. So all that's happening is that the KDC is sending the session key to both A and B. The way it does is it sends it to A and A fords it on to B. And message three, when B receives that, B can decrypt because B has KB. They decrypt and B learns the session key and they can check. This session key is to be shared with user A because inside this third message is the identity of user A. So really what KDC does is generates a session key and distributes to both A and B. And it's just that the second part goes via A. B is certain that this message can be trusted because it's encrypted with the master key and it shared that master key with the KDC. So it knows that the KDC generated this session key. And it knows that the KDC said that this session key KS is to be used with A, no one else. User A could not have modified that message because they didn't have KB. So that's the key distribution steps, those three steps. The last two will go through later for authentication but once that's completed, A knows KS, B knows KS. Now they can take their data and start encrypting using KS to send their data encrypted across the network. So an example of key distribution using KDC. Always a question on the exam about this or something similar, easy one to ask questions about. It captures many concepts in the simple protocol. Any questions on how it works so far? We'll go through four and five in a minute or later. Why is this part? So in question two, KDC sends all of this to A. It's in two parts. Think of the first part is the part that goes to A. The second part is the part that goes to B. And the idea is that inside is of course the session key but also some information to indicate that this in the nonce indicates this response, message two is a response to message one. It's not a replay or we can detect if it's a replay because we would, user A would know the nonce value it sent. B doesn't need this. B doesn't need the nonce value. B doesn't need its own identity. Okay, so why did we include ID, A, ID, B because they were in the first message. That was A telling KDC, please generate a session key for me and B. All B needs is a session key and the identity of the other user. So long as it came from the KDC, B will trust it. So there's authentication happening here as well as secrecy or privacy. Is it a bit clearer now? B doesn't need the first part. It's only for A to check and receive KS. Easy so far. Make sure you're aware of the notation that's used, the identity, a nonce value, encrypt with a, it's clear on the board maybe, encrypt with a key, encrypt with a key, that plain text. And our normal assumptions hold that is you can only successfully decrypt if you have the key. So only A can decrypt the first part and only B can decrypt the second part. And that also provides authentication, yeah? Okay, what are the last two steps? These are just some authentication to check that message three is not a replay. A replay attack involves an attacker taking a previously sent message. Let's say three has been sent to B and they've received that. There's no four or five. Assuming there's no four or five. If three had been sent to B, an attacker can intercept this, but they cannot read the contents because it's encrypted with KB. They cannot read the contents, but they could replay it at some other stage to try and fool B into using it again, possibly because they wanna get B to use the same session key and maybe perform some other attack. Get B to keep using the same insecure session key. So a replay attack involves resending message three. How the attacker can take advantage of that depends on what happens after that. But what the message four and five do is allow A and B to detect if that's a replay. Because what happens if it's a replay, what B does is responds encrypting with KS some other nonce value, N2. So B chooses a random number, N2. Encrypt it with a session key. The attacker should not know the session key. Because the session key was encrypted before, we assume the attacker doesn't know the session key. So B sends this random number encrypted with a session key. Who can decrypt it? The attacker cannot, A can decrypt it because A has the session key. But if A didn't send the first message, it will not reply to message four. It would detect something's gone wrong. So if we don't send message three but we receive message four, then that's an indicator of possibly a replay attack. If A did send message three, B checks. It's like a check saying, did you really send this message? And A sends back a response saying, yes, I really did send message three. And four and five cannot be faked or generated by an attacker because they involve encryption with a session key. And the attacker doesn't know the session key. The idea is that N2, some nonce value, say some random value, the response five, you see on your notes, it's a function of N2. For example, increment N2 by one. And there's no way for the attacker to guess what N2 was. It's a large random number. They cannot guess what it was because it would take a brute force attack. So unless the attacker knows KS, they will not be able to repeat. They will not be able to perform steps four and five to perform a replay attack. So if there is a replay attack, either step or either A will not respond with message five and then B, when they don't receive message five, will detect something went wrong. They'll detect some attack and then take some other approach. So four and five are just there to prevent an attack on some of the replaying messages. Steps one, two, and three are distributing the key. If there was no chance for a replay attack, then I think steps four and five would not be needed. Let's have a break. Let's look at this a bit more after the break and look at some other ways to do key distribution.


Okay, so I work at a new corporation as a DevOps engineer over there. It's been like 14 months for me when we were there and being a part of DevOps team, my daily job looks like working with the developer teams hands on to help them set up their own infrastructure and then maintaining the site reliability of those systems by setting up the monitoring, alerting and bunch of other stuff which helps them like keeping the systems off time for most of the time. That's the kind of my daily job looks like. Otherwise, I love exploring open source even though if I don't contribute to something I just randomly like to just see that more things are happening and just try to learn about it. I love automated, the unautomated thing that's one of my very own kind of for me that I really practice a lot. So that's me. So what would your journey be becoming a DevOps engineer? Okay, so my journey to becoming a to be a DevOps engineer is definitely a roller coaster right? So I graduated in 2016 May and then I had the option to join in this and then I came here and then I was given the option that whether you want to join to some developer team or whether you want to explore something very much and being fresh out of college I just knew that being a developer it means that you have to write some job or create some process and there's something new and definitely there's something much to it. So then I thought, okay, let's give it a shot. And that's how I entered DevOps. And at that point of time we were having a two-member DevOps team. And then most of the things at that point of time were indexed for very infrastructure. So being in DevOps at that point of time with a very fresh hand experience that most of the things had to be set up in place and you had to build things from scratch and then to make it work to the extent that people start respecting DevOps was up to the level that appreciation it deserves. Because at that point of time index was at the stage because people didn't knew that means problems even existed. So DevOps was that kind of workforce and that was a challenge that was actually thrown to us as a part of DevOps team. And being right fresh out of college it was very interesting for us to just be a part of this community and to just be a part of this problem specifically made by DevOps. So yeah, that's how I entered DevOps and so far it has been, Jeremy has been also in my learning rate, he has been exponentially. I have learned typically all those major fancy tech and not just like the fancy tech to be very honest I have learned that how to be a part of a problem and go from right from the bird's eye view to the most distilled level it is being possible. Just by breaking down the problems step by step and then finally figuring it out that okay, this is the root cause of something that has been there for a while and okay, I am the one who actually will solve it.  Yeah, so it's like, I'll tell you right, so it's like being the Batman of the organization to work in finance and your success actually makes the noise. So it's that way. So can you tell a little bit about your talk at this conference today about Plutus? Okay, so in one sentence Plutus is a kind of cost-alerting tool that we have built that actually helped us to keep track of the unknown events that have been So why did we build this? So we had, we were working on a lot of things and cost cutting that we were having we were working on a lot of strategies. So Ashman built a lot of tools that helped us save a lot of cost on universe but certain things that we were quite missing on that let's say there happens to be some of the events in our infrastructure which goes out and people don't come across to know about it So how do we actually keep those things in track? And just prevent those costs to be like being heard on a radio. So that was a motivation that we definitely have to figure out something so that these costs, like these untracked events do not cause the vain cost that we have So that was the kind of tool that then became Plutus it's the serverless architecture tool that helps you monitor all these costs and yeah that's what it does and it's helping us to keep our cost like most stabilized over the last 4 days and average around 100,000 dollar bill on an average on native list because that's kind of a good thing for us and with Plutus being in place, I don't remember being in last past year we have crossed 150,000 for this Very interesting Can you now tell us a little bit about why it should be being in place Do you consider speaking at conferences and community events? Like what motivates you to spend so much time in that work to prepare presentation, to prepare for the talk and then my income comes out where I'm starting to actually deliver the talk From my perspective, so I'm probably amongst the youngest people out here so from a pressure perspective if I have to say something to people who are just starting their career so attending conferences like these and attending meetups like these definitely helps you broaden your horizon because at your current organization you are working on a set of problems set of the challenges that your organization in its business point of view faces and you are solving them which might be right or might not be right problems that you have to solve to see yourself somewhat excelling in the career that you actually want to become but you once actually be a part of the community in which the kind of tech area in which you would like to be a part of then you start exploring the challenges of the problem which other people are also solving this helps you identify that there is something more to it than what I'm currently doing and then you become a part of their problems and they learn from you so it's a kind of a tool way process and it ultimately benefits you a lot in the sense that let's say some of the problems you become and then you become very interested then that can kind of give you a start to explore something very new within your own organization also that this is the kind of challenge problem that you are facing since quite a long time but these are the guys who are solving it let's make a shot and give it a shot and try to solve it now if you take that away from a conference and solve something in your own organization so that is something very useful not only from the company side but also from an individual side also you learn something and you actually help your organization grow that's not a thing that can be great for an engineer thank you for spending time with us we hope you have a very good future


Good morning everyone. How are you doing today? It's very cold. Are you feeling sleepy? Yeah try not to sleep okay because it's still morning so focus. I don't know how the weather is for all the others online but yeah your attention is required so please try to focus okay so let's pray and we will begin. Would anyone like to pray? You can use the mic and pray somebody in class. You can volunteer so I'm not going to say who should pray. Dear Lord I thank you for today's class. I pray that we will all be focused and we'll gain some information. I pray for Pastor Nancy as she teaches us the word give her good guidance and wisdom to deliver the word to us and in Jesus name I pray Amen. Amen Thank you. Thank you for that. Alright so let's move ahead in what we were learning. We were learning about the different kinds of prayers and we talked about, I'll just enlist it for you, prayer of asking and receiving, prayer of supplication, prayer of intercession, prayer of thanksgiving, prayer of consecration, agreement, praying in the spirit or praying in tongues, prayer of repentance, confession, prayer of unburdening and today we will start with the prayer of faith for healing. So when we talk about healing one requirement is for the prayer to be a prayer of faith. Every prayer should be a prayer of faith not just healing but every prayer must be a prayer of faith. However we find that Apostle James specifically states that when we are praying for the healing of someone the prayer that should be prayed should have faith in it. So the passage is given here in our notes James chapter 5 verses 14 through 16 and verse 15 I'll just read verse 15 it says and the prayer of what? Prayer of faith, okay. Prayer of faith will save the sick. So there is an assurance that God has given us when we pray with faith especially for healing. So when we pray for someone who is unwell we know that yes we are praying but faith do we have faith in our hearts that God is a healer and that he can heal the person who has whatever condition. So that is a very important thing carrying faith when we pray particularly for healing. So praying with faith is what will bring recovery to the sick. Now there is another incident given here with the help of Acts chapter 28 it's a time when Paul is on a particular island. He is there and he stays there for a bit and he finds a man who is not well. So in verse 8 of Acts 28 it says and it happened that the father of a Publius lay sick of a fever and dysentery. Paul went into him and prayed and he laid his hands on him and healed him. So what kind of prayer did Paul pray? Obviously it was a prayer of faith and that is why there is healing that happens in the life of this person. So this is something to remember but we will talk maybe more about this in other courses. There is one course only about healing and deliverance. How to minister healing and deliverance. So we will study that course in greater depth. So this is something which is sufficient for now to understand that when we pray for healing we should have faith in our hearts. Now let's move on. The next kind of prayer here is prayer of waiting. So in this prayer we simply wait upon the Lord. What is waiting upon the Lord? Is God late? Is he getting late? Yeah he's never late. He's an on-time God. Time is something that he has designed so you know time doesn't limit him. But what is this wait for the Lord? Wait on the Lord. Wait that's right. With faith.  But my question is why wait? God is testing us. Okay fine go ahead yeah. Patience. Okay God is expecting patience from us. Okay go ahead I'm not saying right or wrong so you can just share your thoughts. God's timing. Sunday says God's timing. Wait on the Lord. We saw that scripture from the Psalms. Wait I say on the Lord. So what is this waiting? Okay prayer. Okay fine. So all of you are thinking along that's wonderful. Lucy says for things to happen at the right time God's plan is perfect. Great. So yes of course we wait on the Lord for the fulfillment of his promises but the kind of waiting in prayer which we are talking about thankfully it's not because you know God is late it's not what happens when we go you know to take a train and you see oh it's delayed by one two hours and then you're waiting waiting waiting that's not the waiting. Waiting in prayer is something completely different waiting in prayer is when you're in the presence of God it's like you are with God and yes we are waiting for answers but it's not so much only for answers it's being with him. You understand just being in the presence of God that is a kind of a waiting where during supernatural you know sometimes worship happens so we are singing but then there are times when we are just there there's no music nobody's praying nobody's saying anything what are those moments those are the moments when you're really waiting God is there you are there you're waiting in the presence of God. It's important for us to have these moments in prayer because something happens to us when we are waiting with the Lord so there are all kinds of prayers different prayers in which we pray we ask we you know request we pray in the spirit so all kinds of prayers we've prayed but there is one kind where we are just with God maybe we are not saying anything but we are just there waiting in the presence of God you could be you could be just you know humming singing or even saying a couple of words that's okay that is still considered as you know waiting in God's presence but the point is we are in God's presence okay and the Bible promises us that when we wait upon the Lord they that wait upon the Lord or we are in God's presence what are the things that take place Isaiah chapter 40 verses 28 to 31 I would like to request somebody to read it it's in the notes but if you can even turn to it from the Bible let's see what happens when we wait upon the Lord yes have you not know have you not heard the everlasting God the Lord the creator of the ends of the earth neither faints nor is weary his understanding is unsearchable he gives power to the weak and to those who have no might he increases strength even the youth shall faint and be weary and the young men shall utterly fall but those who wait on the Lord shall renew their strength they shall mount up with wings like eagles they shall run and not be weary they shall walk and not faint okay thank you for that so this particular passage says that we may go into his presence weak but what does he do when we are in his presence he gives strength right he for those who have no might he increases strength and then it goes on to say that those who wait on the Lord shall renew their strength they shall mount up with wings as eagles they shall run and not be weary so the key point is strength God is saying that when we are in his presence we our weakness will slowly fade away and we will receive a new strength renew their strength okay so this is very powerful so just being in God's presence is changing us it's transforming us from a place of weakness into a place of might or strength so there is something about the human spirit we will study in other courses regarding the spirit of man regarding the soul of man and regarding the body so every human being as per scripture 1st Thessalonians 523 it says that we are spirit soul and body we can only see the body and then we think that it's just the body that exists but you know there is other parts of who we are the spirit man the soul soulish part of us the soul is our mind our will and our emotions I won't get into this teaching it's just so that you are aware so what happens when we wait in the presence of the Lord God's presence affects every part of us so when we say healing sometimes we say we think only about our body and we think oh my body will be strengthened my weakness in the body will go away I'll be strong physically so when we are saying strength strength somewhere our understanding goes to that physical strength but you see there is an emotional man or an emotional person that all of us carry okay so when we say strength God imparts strength to our emotional man or or a soulish man and a soulish man has mind will emotions in our mind our thinking right God imparts strength the way we think the way we understand the way we analyze so our mind receives strength we also receive strength in our emotions maybe so there are all kinds of turmoil we're going through in our emotions maybe something has happened in our life we've had bad experiences we've had challenges growing up so our emotional person gets affected but we don't have to remain there God can give strength God can renew God can transform us into a stronger emotional person so there's a healing that takes place in our emotional man and I said will right what is will will is the capacity to make decisions sometimes our will can be very weak we don't make proper decisions we're scared to make decisions we postpone decisions all these things happen in the area of our will but when we are in the presence of God it affects our soulish man our will can be healed so we receive strength every part of who we are and of course our spirit man we can't see the spirit man but what happens to our spirit man you can imagine you can imagine yourself as maybe see the body we all know we can see the body we look into a mirror you can see yourself but there is another part of you inside you that you can't see which is your spirit man so if you imagine your spirit man as being very weak not being able to really grasp the things of God or fellowship with God just get a picture maybe you know when we say weak you can imagine a weak picture of a weak person but as you wait in the presence of the Lord your spirit man will become stronger and stronger and stronger you're developing your spiritual capacity right so the point is waiting upon the Lord is not wasting time sometimes we feel that hey it's got to be a little more exciting God what is this I'm just waiting I'm just praying I'm just in your presence what's happening God is doing something God is affecting he's affecting my body he's affecting my soul he's affecting my spirit maybe we can't tell now but you see things are being deposited into us that we will realize later hey what happened to me I am feeling stronger I I'm not this kind of a person I'm making better decisions I'm you know feeling strong emotionally what happened the strength of the Lord is being imparted to every part of who I am so that is the prayer of waiting so sometimes like the psalmist says he understood the value of waiting in God's presence he said just wait upon the Lord just be still be still and know that he's got just be there just be with God that in itself is a place where we are drawing strength from God is God strong yeah yeah he's so strong that is why you know Isaiah he writes um he never faints nor is weary right he does not have to sleep he does not have to take a rest he does not have to you know go for a retreat we need all those things because God is so strong he never gets tired okay and when we are with him we are waiting upon the Lord we are not wasting time but many things are happening one is God's strength is being imparted into our being every part of who we are and that is the importance of the prayer of waiting okay is that okay or anything more okay fine so let's move on we'll go to the next part which is the prayer of watching prayer of watching what does it mean when we say watching one connected word is watchman we know a watchman who waits at the entrance of a building to provide security so what is the function of a watchman he allows the right people to come in and he stops the wrong people from entering inside that's his duty so a watchman could stay before the building throughout the day or he could stay throughout the night but there is security which is being provided by the watchman so what is that one quality that a watchman needs to be a good watchman one quality if you have to select a watchman who will you select behavior okay behavior good behavior all that's fine but like one very important quality concentrate excellent alertness alertness is another word so somebody who can concentrate somebody who can focus somebody who can be alert why if they don't have uh alertness what will happen so dangerous anyone can come in they may not check the id card right they'll just say okay you look nice or use you talk nice or come inside gone you never know who that person is uh so alertness concentration focus is the most important thing for a watchman now look at Isaiah chapter 62 verses 6 and 7 um could somebody read it for us non-zing could you please read it Isaiah 62 verses 6 and 7 I have said watchmen on your walls oh Jerusalem they shall never hold your peace day or night you read you read you who make mentions of the Lord do not keep silent and give him to rest till he has to please and till he makes Jerusalem a place in the earth okay thank you so much so you notice here that as I was saying that God has set watchmen on the walls of Jerusalem so those days they had watchmen uh over cities and their responsibility was to stand and watch because the enemies could come uh and if a watchman notices from a far distance that something unusual is taking place he needs to immediately alert um the you know the whoever the king the warriors uh in the nation and then they would go out for war right uh in in in case it is required so uh the bible says that God has placed placed watchmen on the walls of Jerusalem to protect Jerusalem now one understanding that we get from here is that today you and I are the watchmen we are the watchmen that God works through um and especially in the area of prayer so what does that mean as a watchman I have to be alert in prayer so when I pray I can pray for the protection of whether it is my family or my city in this case it's the city so God has placed watchmen on the walls of a city so in the same way you and I when we pray for our city what happens exactly what happens in the case of a watchman the watchman stops some people the watchman allows some people so when we pray for our city what happens is we are stopping spiritual influences which are not good for our city but at the same time we are opening up the door for good spiritual influences or you can say God's work uh upon the city so the bible teaches us that we are the watchmen in prayer so imagine what did we say watchmen must be alert watchmen must have concentration focus the same thing is applicable to us so we need to pray we can pray for ourselves for protection against any kind of you know attack from the evil one or we can pray for protection for our families as I said earlier we can pray for protection for our church for our leadership for the city for the nation for the people and authority so God is calling the church and I say church it's all of us it's our responsibility to pray why because we are the watchmen now if we sleep what will happen if the watchman sleeps terrible terrible mistake so we need to be alert as the church of God and begin to pray always remember that our prayers will protect our prayers will um you know uh allow God's work to happen more powerfully and that is why we are being called as the watchmen over our city uh even at a time when Jesus was in the garden of Getseme he told his disciples it was a difficult time isn't it Jesus knew that he is going to go to the cross and at that time he told his disciples watch and pray meaning pray with alertness but what did the disciples do sleeping yeah I don't know what they were doing the previous day right uh yeah they just exhausted themselves and Jesus told them more than once he said why are you sleeping pray pray but here are these wonderful people happily gone off to sleep okay but Jesus told them you need to watch and pray meaning at a time like this I need your alertness you can't sleep okay or in other words um to be so sensitive and conscious spiritually so when we engage like this what happens whatever purposes God has for us those things will um begin to happen because somebody is there praying yeah we cannot be careless in these matters similarly when a Peter talks about the end times the end times before the return of the Lord Jesus again one point that he emphasizes to the church okay in first Peter chapter 4 and verse 7 um would anyone else be able to read this this one line first Peter 4 verse 7 but the end of all things but the end of all things is at hand so be serious and watchful in your prayer okay sure thank you so much but I think another person was also reading that scripture here that's all right so it says the end of all things is at hand so when things are culminating or they are closing off what does God expect he expects the church to be more prayerful okay so these are the times when we as a church need to be alert in prayer not like the disciples I hope like the disciples Jesus Jesus doesn't look at us and say uh watch and pray you couldn't even pray for one hour would you like Jesus to say that none of us would like that so be alert in prayer and as we do that you know God's protection God's work will happen in our lives so these are all the different categories of prayers today we covered the prayer of faith for healing prayer of waiting and prayer of watching so if there's anything that you would like to discuss regarding this we can and then we will move on to the next section here chapter five right so we have some understanding the most important thing is to use or to apply the different kinds of prayer and see the benefits of it now let's go to chapter five which talks about how to pray a believing prayer so a believing prayer is in the category of the prayer of asking and receiving so when we ask God what is one important ingredient or one important thing that we need in prayer you already gave me the answer I'm just asking you again faith faith yeah faith okay great so faith is what we need and that is why we're calling it how to pray a believing prayer which involves faith so how to pray this prayer there are some points we can consider the first one is to pray with a clear conscience a clear conscience let's read some okay let's just go to one John three versus 21 and 22 I'll ask Amman to read it Amman can you please read one John three 21 and 22 first John chapter three versus 21 and 22 it's towards the end of the New Testament okay are you there yet or sir can I read it it's okay sister we'll just wait for Amman to get it if that's okay with you please yeah thank you so much thank you I have not read written to you because you do not know the truth but because you know it and that no lie Amman could you check if the the number is correct I think you are in one John but the chapter may be different so just check that and then read please sorry ma'am that's okay we love if our hearts yeah perfect not condemn us we have confined confined toward God towards God yes confidence towards God yes move on what's the next was there and whatever we ask we receive from him because we keep his commandments and do those things that we are placing in his side okay great so thank you so it says that we will receive which is verse 22 whatever we ask we receive from him because we keep his commandments and do those things that are pleasing in his side which also shows us that we receive when we are in the right path or we are walking in righteousness we receive right but what does the previous verse say it says if our heart does not condemn us meaning very simple whenever we sit down to pray or whenever we stand up in prayer does our heart tell us anything that is not right you know we call it the the conviction of the Holy Spirit we call it you know our conscience our conscience feels guilty about something or you know we're just not feeling right maybe we said something wrong or maybe we did something wrong or maybe it could even be that we thought something wrong so what happens when when we are when you know we are we're not right with God when we come into God's presence God is holy and God is so holy that the heavenly hosts cry out holy holy holy because there is absolutely nothing evil or wrong or sinful in who God is so even if there's like we come in with something small but our conscience is pricking us what happens it affects our prayer okay so this is very important when I pray for something if there is something that is bothering me I need to repent and say God you know I you're reminding me of this okay I'm sorry I shouldn't have done that I shouldn't have said that I shouldn't have thought that please help me you know to make a change in this particular area so conscience is very important and especially when we are asking God for something because we are talking about a believing prayer now I may ask that God make me a very powerful preacher okay but what about my conscience because only I know why I am asking that prayer it sounds like a good prayer make me a very powerful preacher but maybe in my heart you know I'm thinking that everybody will like me I'll be so famous or I'm saying what else can can we say you know yeah my greatness will be known by all but what's happening here my conscience is not clear or my motive is not clear isn't it prayer is a good prayer prayer is correct but conscience is not clear so that has to be corrected that is when when my conscience is clear then God will hear us isn't it so my conscience should not condemn me so whenever we go to prayer or we go to pray if there's anything that is pricking our heart we need to deal with it right away and then continue in prayer because it's then that the prayer will get served okay so we usually call it like short accounts with God every day that is why Jesus when he taught us how to pray we'll go to that prayer in that prayer he the Lord's prayer it says forgive us our sins as we forgive those who sin against us so every day we may have to pray that prayer because every day we remember I shouldn't have done that you know these things should not have happened so keep short accounts with God and correct ourselves each time and then we come back okay and now talking about conscience if our heart does not condemn us then we have what we ask for so our heart may even condemn us if we are praying wrong prayers like I shared earlier we may pray prayers such as God you know curse that person punish that person or put them down obviously my conscience is not right isn't it my heart will condemn me and say what kind of prayer is this why are you praying this prayer and even though I may use all the principles of prayer it won't work because my heart will condemn me hopefully I will be sensitive enough to recognize that within me okay so this is the first thing a clear conscience okay so when we are walking righteous and when our hearts are clear then God hears our prayer so let's look at first Peter chapter 3 verses 7 and 12 sister get through please go ahead sorry to have interrupted you earlier you can unmute and read please first Peter 3 7 and 12 like not sure if you know she's close to her system maybe someone else online can read it but the heavens and the earth which are now preserved by the same word are reserved for fire until the day of judgment and perdition of ungodly men okay are you reading second Peter or is that first Peter sister I'm looking for first Peter 3 first Peter 3 oh I'm reading the second Peter first Peter 3 7 and 12 husband likewise husbands likewise well with them yes understanding giving honor to the wife as to the weaker vessel and as being as together of the grace of life that your prayers may not be hindered yes next one a verse 12 okay Lucy are you gonna read it I see you sister yeah please please go ahead for the eyes of the Lord are on the righteous and his ears are open to the prayers but the face of the Lord is against those who do evil okay great thank you so verse 12 there first Peter 3 verse 12 it says for the eyes of the Lord are on the righteous and his ears are open to the to their prayers but the face of the Lord is against those who do evil so God listens to our prayers how to get our prayers answered first of all he should listen to it when will he listen to it when we are walking righteous before the Lord but what does it say that he his face is against those who do evil so when we are walking in unrighteousness we may wonder hey how come I've done the course on prayer but God is not answering my prayer however we need to check whether you know we are is there anything that is affecting you know our relationship with God if there's anything that is wrong or unrighteous okay but praise God we learn as far as our identity in Christ is concerned that we are now the righteousness of God in Christ Jesus so every believer we are made righteous by the the sacrifice on the cross all right so that is one thing but of course there is also this additional thing of living the righteous life which is a part of our responsibility so when that happens our conscience again will be very clear and we can be confident that God will answer our prayers now another point over there is verse 7 which is in the context of a marriage where beta says husbands like if there is if husbands don't treat their wives well or 12 with understanding what can happen he's saying that even if this doesn't work out the prayers of the husbands will not be heard okay so God has revealed to us that in in every aspect of our lives we need to walk with the right conscience okay we need to walk in righteousness that's when our prayers become very effective and God is able to answer those prayers so just you know a simple understanding of having a clear conscience now we can move on to the next point here which says ask the father in Jesus name and we've looked at this earlier Jesus taught us before he went to the father he said till now you've not asked me anything but now you ask and you know I will do it for you but ask the father in the name of Jesus so whenever we pray a prayer and you want that prayer to be heard how should we pray it God give me God give me this God give me that amen short prayer God bless this food amen we can you know pray with some reverence first of all and then the next thing is in the name of Jesus because there is power there is authority in the name of Jesus okay there is so much we can learn about the name of Jesus but what happens in our Christian circles somewhere when we say in the name of Jesus it's just an indication that our prayer is going to close now somebody said in the name of Jesus prayer is going to get over praise the Lord you know so but it's beyond that in the name of Jesus means so much more in the name of Jesus is so powerful that your your prayer suddenly has become you know a prayer that God will hear because you have prayed it in the name of Jesus it carries authority it carries power okay when we pray in the name of Jesus so that's very important so when we pray a believing prayer pray it in the name of Jesus so usually we say we pray to the Father in the name of Jesus but this does not mean that we cannot talk to you know the Father or the Son or the Holy Spirit but sometimes we do that we just say dear Jesus or Holy Spirit it's okay it's fine you can pray you can talk to God whichever way but then this is the manner in which God has taught us to pray a believing prayer to pray to the Father what do you want pray to the Father in the name of Jesus okay so that is the second point here the third one is pray according to God's revealed will this is crucial I've shared last time that when we pray our own desires without God's will then we can't expect those things to take place because it's not in the purpose of God for our lives we are only trying to push God or beg God let's say I'm asking God for something it is not in God's will it's it's very difficult to pray like that because somewhere I know God doesn't like this but still I keep saying God please make it happen please make it happen I'm begging him reason is I already know that's not something that God wants to do okay and we don't have any confidence when we pray prayers like this that God would even answer it okay so yeah anyway since most of the young people are sitting in front of me maybe I can share this example that you know particularly when it comes to finding a life partner what does the Bible say you must marry somebody who is in the Lord don't marry an unbeliever don't be unequally yoked to an unbeliever however what happens is you know believing young people they select somebody who is an unbeliever and then they start begging God they say God please please please you know I'll teach them about the Bible and you know I will pray for them I will fast and do everything because your desire is so much that this would work out but in the first place is it God's will that's the question if it is God's will then you pray with confidence but when it's not God's will we know it's the Bible clearly tells us please don't go down that path but we go down the path and then we are begging God but the important part is first of all that we figure out or we understand God what does your word say no what would be the right choice broadly in general what what is the instruction of God's word and then of course you know there are many other things that you know you need to look into in order to make such a big decision for your life but the point I'm making is God's will is something that I must first understand before I before I try to pray a believing prayer so whenever I pray in the will of God it's very much it's very easy because I already know that God wants this to happen then I don't have to struggle so much begging God pleading with God you know doing things like this so similarly many other things in God's word must be understood we need to know the revealed will of God so let's read two passages and then maybe we'll go for a break 1st John chapter 5 verses 14 and 15 so if anybody is there you can ask for the mic and read it yeah 1st John 5 now this is the confidence that we have in him that if we ask anything according to his will we hear us and if we know that he hear us whatever we ask we know that we have the petitions that we have asked for him okay so can you go back again just read it again slowly now this is the confidence that we have in him that if we ask anything according to his will we hear us okay so if we this is the confidence that we have that if we ask according to his will he hears us so the most the first thing that we want from God for our prayers to be answered is he should hear the prayer if it is in his will God will hear the prayer so that's what John is saying he say the confidence we have is that our prayer will get answered because God will hear it as it is in his will so whenever we pray a prayer which is in his will God hears it and when he has heard it we know that he will grant it because it's already in his will but what to do when we don't know the will of God is it possible to always know the will of God silence what is that I can't read your minds so is it possible to always know the will of God maximum voting for no okay no yeah no no okay I think that is the that no wins we're right now so with this suspense let's take a break okay you can have a good break let's come back in 10 minutes and then we'll answer this question all right okay thank you everyone God bless


Now, that means each diaper takes about 500 years. Yeah, I mean, it's strange. I mean, when the numbers I saw, I was like, wow, and you're so unaware about this. So each child contributes to about 900 kg of landfill. Okay, so with me today is Rakhul Preet Singh, the actor and entrepreneur. And as you can see, her background is much more fancy and better than mine. But what we're talking about today is New Boo, which is a very interesting sounding name. She's the co-founder of New Boo. So I'm going to give it over to her. What exactly is this? So you can call me Rakhul. And thanks, Kabir. Yes, thanks. So New Boo is, as the name suggests, it's New Born. And New Boo are reusable diapers, reusable and biodegradable diapers. Now, it's really funny, like when this whole idea came to me, there are two girls who were working on it. And when they brought it to me, I really resonated with it, even though I'm not a mother, I don't have too many kids around, like, you know, even with my friends. But I believe like I'm a citizen of this planet. And that's how it resonated with me. So I learned that each baby requires about 5,000 to 6,000 diapers in the two to three years of the diaper using age. And these diapers are non biodegradable. Now, that means each diaper takes about 500 years. Yeah, I mean, it's strange. I mean, when the numbers I saw, I was like, wow, and you're so unaware about this. So each child contributes to about 900 kg of landfill. That is non biodegradable. That's the number. And with New Boo, you require only 15. So we've made them reusable using cotton and bamboo and everything that's rash free and plastic free and good for the child and good for the planet. And of course, then you save the cost as well, because every parent for an average kid would, you know, the average cost that you save is about 50, 60,000 rupees on your diapering costs. So that was a good, you know, yeah. So that that really resonated with me. And I was like, wow, nobody talks about these things. And it's okay, you know, I mean, we're talking about sustainability today, we're talking about this is this being the need of the hour. We don't have safe water. There's global warming. And then we have so much use of plastic. And there's so many kids being born every day so many. That's how my association with the brand started. And I decided to, you know, be a co founder in it. We launched back in March, and we've got a great response this this much actually, and we've got a great response so far. And yeah, that's all about New Boo. 5000 diapers. Okay. Yeah. So which means, you know, you do the math, Kavir, that each diaper takes about 500 years to decompose. That means wherever the first diaper was made, it's still lying somewhere on this planet. I mean, if you do the math, 500 years, 500 years to decompose. Wow, you never know. I mean, some, some of these celebrity diapers might become collectibles in the future that of course, on a different. How do I actually already answered my next question? How do non biodegradable products harm the environment for somebody who's, you know, getting used to this term for the for the first time? See, like I said, and I used very basic terms. Now if we talk about you want to have a child, but you don't want to give that child a safe world to live in. We're talking about a time where in 2050, if this is how it continues, we won't have clean drinking water. And everything is correlated. So why have children then? I mean, if we cannot give them a planet to have a healthy living, you know, and that's where that's where my support for Nubu came in. And like I said, that anyone who's absolutely new to this term of sustainability or biodegradable, you got to tell them everybody's aware of global warming today. And especially in the cities, you'll be surprised that it's only seven to eight percent of the population that uses diapers, rest are still using cloth at home because it's not affordable. And even then it comes to so much of waste that we are creating. Because we are obviously a very highly populist country. So you know, if you just tell them that one is good for your child, which it is, there's no rash, they're toxic free, they're no plastic. So there's something known as SMA or something that's a polymer of plastic that is put for high absorbency in these non degradable diapers, which is not good for the child, which is what causes the rashes and the irritation and we use bamboo and cotton and everything that's degradable. So yeah, that's I think for any parent, it's easy to understand when it's good for the child and as a consumer, good for the planet. Somebody hearing a term carbon footprint for the first time, how would How would I explain it to them? To them. Wow, that's a tough task. It's going to be tough to explain when if someone who's hearing carbon footprint for the first time, that means that person's absolutely unaware of the sustainability practices or what it is to be right to us, what is planet, what is right, good for the planet. So I think I'll basically start with the definition of explaining how the harmful gases are released from anything that's not sustainable like carbon dioxide and methane and how it comes into play into global warming, into pollution, which is air pollution, we're breathing that we've less oxygen. I mean, you've got to go to the basics to explain it to them, but that's going to be a tough time. Yeah, obviously it's going to take a long time is what you're trying to say. I think in an easier way to tell anyone about any sustainable practice is to really speak about you know, when our grandfathers and grandparents lived, the food they consumed, the nutrition level of the food, the same wheat today is highly made of gluten and is GMO, right? I mean, that's how you explain. So from the food to the water to, I mean, acid rain today. I mean, there's just so many things, the global warming, the summers are getting hotter and the winters are getting cooler and in places like Mumbai, which were not very cold in the winters. And I think you need to explain with examples and how it can really be harmful for the future generations because the planet's not going to sustain if we don't, you know, pull our act together. And I think more than the definition, it's going to have to be the the examples of what could go wrong. I mean, I was recently at IFA and there was this whole water conservation sustainability conversation going on there. And I learned that we won't have drinking water like I was telling you by 2050. That means any child that's born today in a middle age time, I mean, by the time they're like 25, they'll be struggling unless we really, really do something about it. You know, the demand is more, the supply is getting worse. So I just feel that it's now or never. Yeah, in fact, interesting, you mentioned that because I saw this very interesting movie back in 2020, 2021, which released on OTT. Jackie Bagnani was part of it. I think it was called Carbon. I'm forgetting it also. Very well made, very interesting sort of, you know, sort of our version of Black Mirror, what's going to really happen in the future in India, water and oxygen going out of control. That's actually a good movie for people to see, to understand the gravity really. Since we've kept series and movies, what exactly are the upcoming projects, whether it's movies or series, what about it? I think there's one, there's one, something, there's some one fantasy movie which you're part of and there's another one. So there's a, there's one film in Hindi, which is your commercial Masala film, which, yes. So there's one film in Hindi, which I just had a release called I Love You. And now there's another one, which is going to come out maybe end of the year, which is your commercial Najgana, very quintessential Hindi film. And there is a film called Ayalan, which is fantasy, which is the one you're talking about, which is a Tamil film, of course, India, I guess. And then there's Indian 2, which is directed by Shankar Sir, which will also release next year, early next year. These are the films which will release. Indian 2 is the sequel to the Indian if it's released in 1995 or something, the Kamalaasan is going to be part of this project. Yes. Yes. Yes. And he's older now. And? And he's older. And he's older. Yeah. So it's a continuation, it's a sequel for that. Okay, so it's related to the first movie. Okay. Yes, it is. Yes, it is. Okay. Okay. Cool. Thank you. Thank you so much, Rukul, for talking to us. The Wi-Fi has definitely spoiled sport, but still quite an informative session. I mean, it is actually a responsibility right now for anybody who's applying to get children into this world at 30 years later, what exactly might be. And hence, I think these products which are into sustainability and thinking about the environment and the future are actually walking the talk. So to say, instead of just getting views on TEDx speeches, this is actually something which is getting stuff done. Thank you so much. Thank you so much, Rukul. Thank you.