Great. How's your week? Very normal, normal week. Any fun things? Any, any exams? Things like this? No, no, everything has passed. So so just nothing special. Okay, any did you cover any new topics this week that you need help with or anything like computer science or Yeah in computer science in general? No, nothing too much. There's another still doing Python. Python how are you feeling with Python? Pretty easy. Pretty easy. Okay, anything because I mean, we went through like four loops or while loops, but you seem to have those under control. So if you want this today, we can do more security. So cyber security Yeah. Last time you showed me some code, how's your game engine going? Fix the rendering problem and note sort of can Yeah it can render now and I'm trying to make it except textures outside of the not outside, but not trying to make it just except not built in textures. I see for some reason it only Ted accepts built in tecshows from gltf files. Okay, but can't you just add your own gl files? No, no, it's gltf is a file format, gll transform format or something. And you can just as if your own or is it I mean, because I'm not that good at modeling, so I have to download three assets for I see a common problem in video game design. Tough because Yeah if you you have a good idea for a video game, but then you need to actually draw it or make it. I know how to do a cuue. I know how to add a texture, but when it comes to complicated stuff, I'm just not an expert at it. So not yet. Soon, soon. Okay. Well, today I was just going to do a bit more cybersecurity. I know it's not the most passionating. Pason topic security, but it's necessary in your course. One question I have is. Do you want to do stuff related to your course or do you want to learn more about computer science in general? What's your interest in in doing these tutorilessons? I would like to finish my course while learning something more that can be sounds like not just strictly to the syllabus, maybe something outside of a place to place. Okay, then let's get your syllabus up and let's do up until 430. Let's do some more security stuff to make sure you really got it. You're almost there. So let's really just make sure you understand the differences because you will get some, some some some kind of questions on this. And then let's spend the rest of the time maybe talking about, I mean, there's a lot we can talk about threats, we can talk about Python, we can talk about game design, the slash systems, right? That's another thing we can talk about. We can talk as well about unix, right? That's going to be Linux systems. You've got as well just coding in general, which is harder to do here because in Python two, because we just don't have an environment where we can code properly. And then you've got web algorithmics, which is interesting, but depending on which kind of person you are, this can be quite fun. Yeah so there's a lot we can do, but also a lot we can't do. So. So if you want, we can start with the course and then switch to something around here. Yeah, cool. All right. So tell me what's farming? Getting information by by obviously disguising itself as a proper proper ip proper domain and then getting information and then prompting information. Yes, perfect. Last time I told you that farming is going to be a website looks very similar so like there's gonna to be www or something right and maybe I'll be Google with one only one zero so you won't get suspicious. Another thing that people do is what they do is they, let's say you have an email, or not even an email, but like you download something right on from web page and you download something. And what this can do is when you click this button here, it downloads a piece of software onto your computer that has actually a fish farming. Right farming virus. And what it does is it changes the dns records. On your computer. So do you remember what dns is? I know you do. But just checking domain name service. Yes, domain name service. And what do they do? I maa, domain to a ip, exactly. So you've got a domain. So here, let's say you've got Google amap. Two, like one, two, 3.4, maybe. And what this virus does is it comes here and it changes it to maybe like six, five, three, two, breso, even on your computer, you're gonna to go to Google, and here on the top, it's gonna to say www dot Google com. But it's not going it's not going to redirect you to actual Google. It's going to redirect you to this fake Google. And so you're going to think you're on the real Google, and it's going to look like you're on the real Google because theysay Google dot com, but you'll actually be on this fake ip. Yeah, that's another trick of farming. All right. Very nice. What about fishing? To scan someone. Yeah any more anything more specific direct. Obtaininformation by direct contact communication. Yeah, exactly. So it's something like an sms email, right? Itlook legit, but it's not. So it's like a fishing email scan. And you sometimes they ask, how can you detect a phishing email? Theysay things like the answer Marks says something like bad English, or maybe low on details on details, or maybe theysay something like asking for passwords. No one will ever ask your passwords or passwords, right? So so these are all the the the things that are done on fishing emails. Cucku, what about a worm? You know what that is? Yeah, it's a malware that is sent through the Internet to computer computer and it replicates. Yeah. Very nice everywhere. What about a virus? What's a virus? What's the definition of a virus? It's a type of malware that's. Download it and can corrupt or no, can just run on your operating system and do something for that. You notice. Yeah, exactly. So it disrupts the system, disrupts system, does what it mainly does plus copies itself. Okay, very nice. What's the difference between what's a dos attack? Distributed a denial of service? Yes. What does it consist of? A computer is sending malinformation to a server. Yeah. So you're sending what's called malformed. Data to a server to crash it. Very nice. And what about a DDoS distributed to all services using main computers to overload the order set cell phone data to a server? Yes. And are these normcomputers that I just go out and buy? Or how do we get lots of computers to do this by Mawer maer? A virus and we call it a rats remotes, remotes access and then here toolkit. Very nice as dgos. That's farming, okay? Very nice social engineering. Have you heard of that term before? This is getting massive actually. So let's say. Imagine I wanted to get into someone's house, right? And I contacted, it's not my house. And I contacted locksmith breand. I told them, Hey, I'm X, I'm this person's black brother, uncle, maybe a child, whatever. And I'd love to get into your home, into into my home. I've been locked out, right? I've been locked out. I don't have my keys, whatever. Like I can't, I don't have any documents on me. So I can't prove who I am, but I'm really stressed. I want na go. I just want to go home. I have to have an exam very soon. I to get my stuff and leave right. If you, if you call someone and you do that, it's called social engineering because you are exploiting human weaknesses in a system. Yeah. Human weakness. Do you have any examples of social engineering? Scam calls, scam calls, very nice. Scam calls. Anything else? No select bank, bank detail, bank details, like you could go for bank details, things like that. And with AI, this is becoming huge because I don't know if you've seen you can copy someone's voice now you only need like 10s of a voice. So it's becoming very common. Well, it's becoming more common for AI to mimic people. And what they might do, for example, if if example, what they might do for parents is they might record some, the voice of the child for x amount of time, and then they might use the voice of the child to train an AI and then call the parents and ask for money for x of reason, right, or vice versa. Or ask, like copy the voice of a friend and use that to call them and ask for money or something, basically a scam call. So that's social engineering. You know what brute force is, okay? What's adwear are? Just displace advertisements on your computer. Yep, adds everywhere. Very nice Trojan horse. It disguises itself as a normal application, but operates. Operates that nowhere under the hood. Very nice. Okay, great. All right. So m. How would you protect yourself? So Yep, firewall very good. What does that protect you from? Do firewall. Or DDoS, for example, or dos what else? Or does it block station and environment fishing less? You can put hacking here. Hacking is gaining access to a system. Hacking and viruses. Viruses. Well, that's so far then antivirus, what does that help with any type of power el anymore? Malwhere, but probably not DDoS or dos right? Because these are different. Very nice. What? Like if I were to ask you how to protect accounts. How would you protect your accounts? Like, for example, step verification. Yep, very nice. Two steps. Verify. Yep. What else? Biometrics. Metrics is a big one. So your fingerprint, for example, longer password. You can use a password manager. Sometimes they allow that password manager. Right, password manager, okay, have you heard of ssl? In what context though, in the unfortunately context of your of your sylbus, let me see what I can find on ssl. You have you have a very small portion. So I'm kind of wondering. How important how much do you need to know about the ssl? Okay, okay, you need to know a few things. What do you know by sl? Don't know nothing. I don't know anything. Oh, you don't know anything, you're think. Okay, no problem. It's basically it's secure. Sosecure software license, who almost sock it layer, sock it stoit layer. What this does is kind of it encrypts data over the the Internet to kind of stop eavesdropping and tampering. And basically it's used to like protect websites or like payments and stuff, and it happens on the web browser. So and then you'll hear about its brother or successor, tls. We've maybe talked about this before. You might maybe know what tls stands for. No where is it transport or something? Yeah, transport sports. I think you said that transport sports out. I don't know, layer that's not the Transport Layer Security. Transport Layer Security. So usually people talk about ssl slash tls because they kind of are the same slash merged tls as kind of the successor, but they're kind of similar. And what it does is have you seen have you ever been to a website that's like this http slash slash right? Whatever. And this gives you a warning. Basically it says Oh you're not secure you know it's be careful this is because it's not https https uses ssl and tls, right? And what it does is okay okay what it does is it adds security to the website so you already know about public key and private key so I'm not going to go into that but it basically uses a very very similar similar message here. Yeah very misma design. Sorry. So you to say you joined an https server, I'd say you've got your server here s and you've got your client here, see? And then you've got another thing called the ca, which is the certificate. Authority. Here like this om. Let's say you want to connect to this using https server going to you want to connect to this and the server is going to reply, okay, Yeah, I want to connect remember the tls thing? It's like, please, it's like I send you a packet, you send over, I send over, right? So it's using that kind of firmware, the server replies with a certificate. And public key. Then the client will talk to the certificate authority. Now these are centralized components. So you've got a few big ones that forget their names, but it's like a centralized repo. Basically it's a centralized repo of data and and basically just a big list about the information on the website and it gets you a certificate and a signature. So what you do is you get the certificate from the website. The website has a certificate and it sends it to the client. And this has also its public key and a bunch of other details. And here the client will say, okay, I'm going to check if your certificate is valid. So it's going to go to the ca. Here it's going to go to the certificate authority. The certificate authority will basically check if the certificate is valid using its own public key. So it's got its own public key. So it's going to basically decrypt the certificates using its public hebecause. A certificate is given by the ca to the server. Certificate with encrypt from ca. This this step here, this step here, let's call this s one x. This step is only done once, like way before. So certificate is just held somewhere here. C, right? So the certificate is sent, the client checks with its certificate authority if it's valid. The ca says, Yep, no problem, go for it. Valid. And so this, the client knows that it's on the right websites. You know that this website is valid, there's no problems, and then it sets up a https connection. And so here what happens is using the public key here from this one, a will send it. Okay, here's your data. And here it will send a session key. And the server will say, okay, Yep, let's use this key, okay. And a tls connection established. But if there is a session key, can't others use up? Good question. This session key is encrypted with Clients Public. So what you do is the clients here, it sends https and it sends its public key, right? And the server encrypts, it sends back its own certificate and public key. And so the clients, when it sends the session key, it's encrypted with its public key. So here, so you decrypt session. With a private key. Because this is encrypted with the server. Sorry, I put clients here as reserver. I don't know if I can delete that, it's too small, but this is basically so let me see if I can maybe like this. So Yeah. So this is session key encrypted with server. Right. So your basically clients encrypts the key with the serverpublic key and then sends it back to the server, which it can then decrypt it because it's got its own private key and they start communicating on a session key because it's just quicker. Does that make sense? Especially the thing with the central authority, the ca Yeah this step here, this centralized repo is done once or it's done like done once per month because the whole point is that the certificate is valid for a certain time period. So when you see certificate expired error, it's because the server you're trying to connect to hasn't renewed their certificate. Or it's because the certificate authority, for example, if you are in China or if you are in another country, say Iran or Russia, they might not have the certificate authority, might not have the website you have because they might be, for example, in the United States or in the uk, or in France or in Germany. So it's also country based too. It's not just centralized over the whole Internet. It's country and company based. All right, so you got that nice ssl. Do you know the proxis proxy server? Yeah. It sets up a private network. Yeah, a downgraded bclean n, Yeah, like a worvpn. Yeah. Yeah, it's like a downgraded vpn. Very nice. Okay. So if feel confident replying stuff about about proxy service. No, I've not looked at it that much, okay? Let me make sure that I'm not missing anything in case there's something interesting. So you know that it's an intermediary between a client and a server, and it's used to basically add a Layer Protection before before reaches the client. Yes. And it can use against, for example, censorship. There's another point here, censorship and georestrictions. Right? And this is actually important in more important than ever because you have different laws everywhere now on the Internet. So you have to maybe use sometimes a proxy or a vpn to access content you can't otherwise. Okay, very nice. Let's keep going for a bit and see. All right. What about automated systems? You know much about automated systems. No. Things like sensors, stuff like that. Basically, in an automated system, the way they want you to have it is you have a sensor, s sensor, which gathers data from the outside world. Then this links to the microprocessor emc. Microprocessor. And then this microprocessor establishes rules. So do x if y. And the y it does is with actuators. So I'm gonna to try and draw a gear. Let's see if I can do it. Oh, that is uwe. Can I do it? Oh, no, it's bad. This will turn actuators, right? Actuators. And this could be anything from like a machine to pump to like light. Or sound, that's an actuator. It's some kind of outputs in the real world and it's a loop that goes on for our wherber loop wherever. Sorry, so could you repeat what the mc is? Yes, this is the microprocessor. Hello. Just call it microprocessor. Mc is probably not this mp, but microprocessor is just what does these rules and what it basically processes data from the sensor, so takes in sensor data and then converts it to digital data. That's what you have seen in the exam. So digitize. So. Collect data, collect, then it digitize, then you go through like if X, Y, whatever. So it depends on the condition. So if the water level is above x, or if the light level is above x, or if the sound level is below y, right, then activate, move some kind of actuator. So send signal, send signal and do forever, or do for a specified amount of time. They might say, for example, during the day, right? So then say during this hour to this hour, do that, right? So that's kind of what they want when they ask you microprocessor questions or like automated system questions. Okay, so let's move on to the second part of the class. Let's go back up here. I suggested a few different things, right? Python game design, unix coding, web algorithics tratrading not trading, but like. Numerics. In comsai, right? There's one I can do here. What would interests you and what would you like to learn? Design or algorithm. Yeah, Alrighty. Okay. So there's the way I like doing algorithics is by sharing my screen and doing problems with you. And in fact, it's the way, it's the best way to learn algorithms. Unfortunately, we cannot share screens. You are able to share screens. We are we are able to. Okay, how do we do that? I think you are. I don't know. I don't have the teacher's interface, but I saw another teacher share screen. So okay, let's I'm going to try and do it. I'm going to try and do it. Let's let's see if I can do it. I'm going to spend three, four minutes trying to figure this out. And if I can't, then we're just gonna to have to move on because I don't want to spend too much time on this. Super. Juback. Sorry about that. All right, made me laugh way too hard. Okay, let's see. I. Think there's a drive or something. There's a class room drive and people drive. Yeah maybe could you like give me the permission? Yeah, Yeah I'm going to give you permission. In fact, it's better if you share screen anyway, so I'm gonna to give you permission. Here you go. No, I cannot. Teaching tobox catches let's stop sharing student desktop sharing send request. I they can let's go very nice. Okay, amazing. I. I opened reabout that. I'm actually going to ask you to so maybe we can work on your project a bit later, unless that's what you want to work on, but we could do some algorithics. Have you heard about leacode? Now would you mind going to chrow? Or edge or whatever. And Oh, you speak you speak mandarin. Yeah wait, wait, wait. Sure. I don't forget what I said now I used to speak decent amount of I forgot now sure win or sure John win. I forgot to say a little bit. It's all gone now. Yeah a little bit depth. Lead code. Lead code. Licode right there a licode is A L ecode. There we go. Wait, this one. Yep, that one right there now. Yep, the first. No, no, that not this one. Go back. This one here. Oh, wait, no, no, that one, their leacode the world's leading online platform. All right, I would really suggest you create an account. So if you wouldn't mind creating an account very quickly, if you can't, it's you're gonna to use this for a long time, especially if you. Reasonname cannot be what? Or you should probably use like complicated Henry if makes a complicated username, if that makes sense. What's only conto locate? Very nice learn just click learn next and hopefully to ask you Oh I don't no offense but it's it's tough man it's it's hard I should okay. Oh you're anyway, it doesn't matter okay those are problems. On the top part, on the top bar. All right, now, if ever you want to get a job in computer science, this is how you do it. Now obviously, I know you don't want na do that, but this is where we can learn some algorithmics. Let's go to longest common prefix, number 14. Number 14, yes. So the way this works is it's a bit like, Oh no, you don't have to subscribe. No, it's completely free, so you don't have to subscribe. So basically what c plus or what's least ds code is, it's a world leaderboard of the best programmers. And the way they do that is they have problems, coding problems. And some people absolutely love it. Some people absolutely hate it. And I'm here for you to enjoy yourself and to learn, right? So if you don't like it, then you shouldn't do it. But what's good about this is that you're gonna to learn a lot and you become very employable if every want to be employed in computer science. Now I'm not saying you want to get a job in computer science, but it's good for that and it will teach you. Now of course, the easy questions are easy. The medium ones teach you data structures, and I'll be able to teach you data structures with them. But the hard questions, like they're quite detailed brain teasers and especially in physics at the moment, of course, if you're in research, you'll never have to do leds code. But if ever you join, for example, a defense company or or for example, you want to become some kind of engineer, they're all they're gonna to ask you these kind of questions. So it's not a lost and it depends what you want na do, but sometimes it's just fun as well. So if you're into tuiyou're into it, so all right, I'll let you read the question and see if you understand. Let me know if you have any questions and then we can maybe do this one is it should be decently quick. Let me know what you think. Yeah, I think it's quite nice. I just don't like the fact that it doesn't use standard. Standard Yeah I just Oh object is filled with this. It's. You can change the code as well if you want to practice your Python, if you want to practice whatever you're most comfortable with. I don't think I'm good at algorithms. No, no, no, don't worry about it. Do not worry about it all. Okay, so write a function to find the longest common prefreak starting with amongst an array of streams or the for these kind of questions, think about how you would do in your head, right? How would you find the longest common prefix? Do you know what the common prefix? Es? Yeah and it's just the sois. Yes, very nice. What are your thoughts? Talk to me. Let me know. Let me know what you're thinking so I can sit. I'm thinking of setting up a for you straight away. Just kind of compare it every time. With done那。Supposed to be the longest character though, the longest prefix, common prefix. So what's the longest amount of vision? While while we know I'm thinking of the shortest character in the string, the and the vector one, we're thinking more about the starting characters, right? Like what's the longest prefix? Substring. So how many characters are the starts that are uncommon for all the strings? Yeah. Yeah. But if they're are no in common, then it might get starso. Yeah, very good point. How would you do this in real life? The shortest character, the shortest word, the length of the shortest word. But. I'm not even sure, but I just. So let just iterate through every one of them and get the dot size. You could do that. But what how would that solve your problem if you have the slowest one? Wait, if you go back, Yeah. So like for example, this one I would get four and then I would iterate to that and then find that. So the I here would be four. So you find the lowest one and then iterate through it to see what's in common with the other. That's probably not the most efficient way. But no, it's a way. It's a way. The idea here is to solve it first, then optimize always. Rdom, ably, maybe I don't know what I'm doing for no. Wait, push shback. Not sure I think pushback sounds right. No, but because it pushes it to the back, so it shoits, I know I push back. Yeah. Yeah, that's the whole thing. All right. Press run. On the on the top left, there's a submit button. Don't click the submit button ttons, click the arrow button first. Yeah or it's asking to verify your email. Yeah. Hi, America, I think you have to go to your email and then you can, you can do it there. Oh, I hope it's. Irdon't, Oh, that's due to I think, Yeah. Oh, you have confirmed. It's confirmed. No, you might have to reload the other page. I to verify, but it doesn't say anywhere to verify. I think it's I think it's verified already. Yeah, Yeah. I think you can if you go back to the previous page. I think keep going. I think you should be good now to Press run. Let's. See. Okay. No. I you know the language good enough size too much of this the size or size string ger like. I mean, it has like 20 of these like just kind of size of and there's length, there's size. Yeah it's not very easy. C++. It's renowned for being a tough, tough language. Okay, almost. So what do you think went wrong here? Basically here it's telling you, you almost got it right. You got fl but you didn't get fl. Oh no. So here you were supposed to get a thought, but unfortunately the output was empty. So what could you change here to so the with my output, your output is just there. So you've got strings and an output and then expected there. So expected fl, but you got an empty string. I okay, but this works okay because it doesn't print anything. So here there's something in your codes that's not quite right, which means it's that it's that it's failing somewhere. Just to let you know the length of strings can be infinite or not infinite. It can be up to 200. So here on the left you've got constraints Yeah and then you you have it can be quite long. Sure that string has something else in length. I think. There's length or length here. How you this size that? Oh, okay. It's kind of and I didn't know if it has that function. Thatbe useful. Oh, it's this. So that size, it's great though. If you go to your codes, first you find, basically you find the lonthe longest string, right, or the the size of the longest string. Then you go through each of the strings or the, you look at the, the maximum size of the string, and then you look at string zero, string one and string two, and you see if they are equal to each other. And then if they are, then you add it to the end. I'm wondering here here you do. R dot buffer pushback strings zero. I Yeah because it's this one controls the character. This one could say I think it's correct though starts at zero plus plus I dot one probably be because n buffer is zero somehow. If it's zero, it cannot be small. No, no, I have to set it to no, I have to set it to some larger value. Massive numbers compares the sides. That's why. Smart. There we go. You got it. Our close output n buffer is a very large b dot size is less than n buffer b dot size. Otherwise n buffer you can always print values, by the way, so you can put like a print or like a system out for n buffer or print f for n buffer if you're not and see if that's the error. Wait, is this seven right now? Okay. It's not it's not using the latest version. 64, four. So it looks like it's that. Then in your four loop I'm looking for into I equals zero. I is greater than n buff. It should be. I is less than n buffer. Now I think that might help as well. Okay very nice good job. But now I'm going to give you the bad news strings can be up to 200 long it's not necessarily just three items so if you submit this code it's is gonna to test it up to 200 items and strings where I don't think your code will work unfortunately as we're only looking at the first and the second and the third element. So there's some food for thought for you there. I just want to to start wrapping up the lesson because we're getting to the end personally. What do you think of this this leak code? I know it's good practice. It's good practice. I know it's unconventional. Some people love it. Some people hate it. If you're part of the people that love it, then I'd love to do this with you. We can spend 30 minutes every lesson and we'll just do some lecode problems. I encourage you do some on your in your spare time. You'll become really good if you do them every day. But Yeah, so we can we can do that if you enjoy it or we can do some coding. We can do whatever you want now that we have this shescreen ability. Yeah the world is our oyster, right? So we're free if that makes sense. So what do you think? Yeah, thank it's and I could do some at home and if I find a hard one, could I could ask you to help, of course. Yeah. Now I want to preface this by saying they get really hard. So the easy ones are tough at first, then you crack them easily and then it's fine. The mediums, they go from medium easy to medium hard and they can be really tough. And the hard questions can be really hard. So I know my ego always got to me and I would say, Oh, I'm gonna to do a hard question. I'm going to figure it out. And then I would spend four hours on it and then I would end the day on a sad noso. Make sure to start with the ec ones s, even though they might look trivial. Some of them have a few catches. And then really the meats and potatoes is all in the mediums, right? You're where you're gonna to learn data structures, but you're gonna to urine hash maps, dynamic programming, boom, boom, boom. That's where you're going to expand your thinking. And and we can work on that together if you want. Awesome. Any last questions? We don't have that much time left, so I don't think it's worth really doing much. Any questions? I don't have any other questions. Okay. Well, okay, let me see if I can end this screen and the screen chaso. Okay, so we saw a bunch of stuff, automated systems, proxies, probably key central authority. This is important, ssl tls, antivirruses, firewalls, adwres, ddodos, worms, viruses, and how to spot spofishing and farming attacks as well as dns, how it changes with a virus, how it changes the p in your own dns so you get scammed. All right, have a good week, Henry. And let's let's do some more Leo, next week. Yeah. Thank you, sir. Bye, bye, bye. See you.