Lecture 24: Man-in-the-middle Attack, Certificates and PKI by Christof Paar

For slides, a problem set and more on learning cryptography, visit www.crypto-textbook.com

[@paddmin]

spent over 8 years in college and grad school and these lectures by far were the best lectures I've ever had

[@vladimirsivcev3064]

Dear professor, you are the definition of how teaching should be done. I cannot stress enough how thankful I am for your lectures. I wish I could attend all of your classes, to learn as much as I can from you! Thank you!

[@bharatchoudhury676]

Hello Dr Paar, Thanks for putting this out there. These lectures are awesome and kept me super engaged. You have a talent for explaining things elegantly and simply this free high-quality knowledge being out there is a huge gift for everyone.

[@futurDaFutur]

Dear Professor Paar. Thank you so much ! This lectures were wonderful and I've had great time watching them (and read the book in parallel). Looking forward for more. Thanks and keep up on waking up students :-)

[@jameskatende3665]

Had to teach crypto to some people and I never attended a crypto class before. Your book and videos are very well done. I have mathematical background and I like the way the math is packaged in your book. Just the basic minimum and no side shows, but sufficient to understand the mathematical background required. I particularly like the way quotient rings are introduced (In AES) without mentioning them by name. Of course one can go out and read more math but this book has figured out the best of both worlds. Some books and online notes go a little deeper with the math but you found the perfect balance. One just needs to be a little patient with the book. Now going over to the crypto website to play around with the other tools and resources. Your book is great and I now have some fancy applications to add to my abstract algebra classes. Thank you and God bless you.

[@introductiontocryptography4223]

I am glad the videos are of help. Thanks also for the kind words, that's a great encouragement. Good luck with your course(s). cheers, christof

[@sreyasnampoothiri]

@@introductiontocryptography4223 Is the a book which i can get a deeper look into the math behind cryptography?

[@clivea99]

Many thanks prof for your lectures; I watched the entire series. You have a natural ease in communicating the essential ideas to your students.

[@praagyadhungel1357]

Dear Professor Paar, Just wanted to drop a quick note to say a huge thanks for putting your lecture on KZbin! 🙌 Your video was seriously a game-changer for me. The way you explained things made it so much easier to grasp, and I'm feeling way more confident about the topic now. It's awesome that you're sharing this kind of quality content for free. Your passion for teaching really comes through, and it's making a big difference for learners like me. Cheers

[@introductiontocryptography4223]

Thanks so much for the positive feedback, this is very encouraging.

[@Fleischegutt]

Professor Paar, thank you so much for making these lectures available to the public. You have taught me a lot.

[@ramkumarnj7617]

Thanks a ton Prof. Paar! Your lectures were of great help for my M.Tech. I also loved the way you delivered - the way you motivated and the way you ensure student's attention. Ultimate!! Hats off!!

[@Robert-me7ce]

Thank you Prof. Paar for sharing the lecture to the public. It is very helpful.

[@sobiaasif6319]

Dear Professor Christof Paar, I am doing a Master's Program at Hector School, KIT. We had a module in Safety and Security in IT and I had to give my exam on it. Your 24 videos cover almost each and every topic and much more in detail what we studied at Hector School. I went through each and every video almost 5 to 6 times and passed my exam with a very good grade. I am very thankful and grateful to you for putting this immense knowledge of yours in Safety and Security on you tube which is benefitting thousands around the world. Does your book or lectures also cover the concept of key and encryption decryption functions, the role each plays and how they are differentiated from each other. Thanking you and best regards.

[@dpraajz]

3:05 Introduction to Asymmetric Key Establishment 9:40 Man-in-the-Middle-Attack 43:10 Certificates

[@EssamAhmed-kk4xg]

I wish I go back in time and attend one of your lectures as a student. Thank you for everything.

[@emmyzhou9552]

Thank you so much for these brilliant lectures! I have now finished watching all of them and I must say that they have really sparked my interest in cryptography.

[@den1fednu]

Watched all the lectures, awesome content, thank you for making these available to the community

[@rishab.huihui]

Thanks a lot Professor Paar. Great lectures, I watched the entire series. Best video lectures on the web probably! Looking forward to any updates on the series.

[@SkatEirinn]

Brilliant series, i've watched each lecture and its made me very interested in cryptography

[@HahuMelody]

Dear professor christof,, you are special,I really love your lecture and your teaching method is more than enough, infinity wonderful lecture...

[@asmitadhikari1472]

I'm now more interested in Cryptography and all thanks to Professor Paar who made cryptography simple.This whole series feels like a netflix show and I got goosebumps at the end :D

[@praagyadhungel1357]

I FEEL SO POWERFUL AFTER LEARNING ALL THIS!!!

[@tsasa192]

You are very good teacher! Thank you! Wish you all the best!

[@davelloyd-]

Thank you so much for publishing this course. I am studying through distance education and our assigned coursebook is very very dry and difficult. Your lectures are so much easier to comprehend.

[@mojtababisheh7915]

You are awesome. I like the way you teach and you are also very good at what you are doing! Thanks a lot!

[@PhatPazzo]

Thank you very much for this series of videos. Even for someone with a strong interest in cryptography, you gave me some insights into stuff I had missed in my own studies. I wish I had seen these videos earlier, it would definitely have triggered my crypto interest earlier :)

[@BarrettKillz]

Went through all the lectures before the examination (we have a very similar curriculum, though all in one semester). It was truly an awesome refresher. Thank you!

[@BarrettKillz]

Update. Got the maximum grade, been rated top performance. I cannot thank you enough, sir.

[@kaloyanmanev]

A big thanks! It was really interesting, and I learned a lot! I just finished the series... The feeling is the same as when you finish of a very good book. I hope that in future there will be more published courses by professor Paar.

[@damianofranzo5547]

Dear professor, i watched the entire course, these lectures are wonderful, thank you for everything. Have you planned to upload the next course? in one of your comment you said that maybe you would have done it in the early 2017, are there any news?

[@KamiK4ze]

yeah - honestly he made a really hard module easy to understand. I never found it interesting with my lecturer but now I'm thinking of buying the book even after the exam just to learn more :D

[@ColinToal]

I love these lectures. Thank you for posting these. I am always awake and not doing facebook.

[@zakichan-r8c]

Dear Professor Paar Even if I Fail in My Examen , you are awsome , we love you.

[@ikechukwumichael1383]

Thank you for these amazing lecture series.

[@chelseafcrk2629]

Great help......u r vedios are awesome .......u r the best!!!

[@elabeddhahbi3301]

thx so much 4 sharing this knowledge ,i m really looking forward to see u again in another courses and trust me we glad to having u as teacher

[@praagyadhungel1357]

I CAN'T THANK YOU ENOUGH PROFESSOR.

[@amadouthiernobah6071]

Thank you sir for you service, I have learned a lot.

[@riebeck1986]

Thank you for these lectures !!

[@halildogan6435]

Thank you Professor, great lectures.

[@Maiiepmaidiep2610]

thank you very much professor! I have learned a lot from you.

[@sathyamurthisadhasivan6275]

Hello Prof. Paar, Thank you for your course series. You are doing invaluable service to many of us by providing them to us free. Combined with your book, these videos are a great help! I am requesting you to see, if you plan to offer recorded classes/courses which we can watch, on Post-Quantum Cryptography, specifically the CNSA 2.0 Algorithms suite? It will be a great help as these algorithms are becoming a must need in cryptographic design implementations. Thank you for anything you can offer. Much appreciate your time and help. - Sadha.

[@introductiontocryptography4223]

I might or might not teach 2 new lecture on PQC in the summer semester of 2025. If so, they would go online in appr. June 2025. Best, christof

[@sathyamurthisadhasivan6275]

Thank you, Sir. PQC is becoming a must needed functionality with the mission critical customers we are dealing with. It is being considered essential in the devices which are going to be deployed by end of 2025. In fact, current contracts with these customers stipulates conformity & availability of CNSA 2.0 algorithms in the product cryptographic suite. I really hope you will consider offering PQC courses as you suggested and I very much look forward to the content at the same premium level you have offered in your other courses. Thank you so much from all of us who follow your course material and for offering them.

[@filips1218]

Thank you Christof.

[@abusadatmohammadsayem1311]

Is there are any other ways to say except thank you professor Paar. Hope to visit you someday, for the knowledge and passion you have for this subject. I wish my computer network security professor were active like you. Whatever I have learned this semester is because of your book and video lecture. If you write in any blog please share.

[@samoldfield9997]

Thank you sir for this great course which you made it available.

[@RoDrop]

Another great lecture. Thanks

[@chelseafcrk2629]

desperately waiting for ur Advanced crypto vids!

[@saadiComsian]

Thanks a lot for the great lecture!!

[@MazenAwaraa-yk1ts]

Thank you for your efforts

[@songzh2911]

Dear Paar, your lecture is so wonderful and I bought the textbook you wrote. I suppose that If we can get some Openssl command hands on, it will be greater!!

[@mrmosk2011]

I went through all the lectures. Thank you Prof. Paar for a well design and presented course. I already bought the book and it will be my primary reference book on these topics. In the video, I heard Prof. Paar mentioned there are a few more classes after this, probably more on some practical applications. Can we see those as well?

[@introductiontocryptography4223]

Thanks for your interest. Unfortunately, these are the only classes that are available with video. However, the lecture notes for my follow-up class "Implementation of Cryptographic Schemes" are available for free. You can download them at: www.emsec.ruhr-uni-bochum.de/teaching/literature/ Look and feel is similar to Understanding Cryptography. However, the lecture notes are not as polished as the book :) Enjoy learning crypto, christof

[@mrmosk2011]

@@introductiontocryptography4223 Thank you very much!

[@PhuNguyen-bi7pi]

Thank you very much. Hope to see your future videos soon. I also get your book.

[@ignitedroads]

Thank you so much sir. it helped me a lot.

[@AndrewSmith-pn2qc]

Thank you Professor Paar! Would it be possible to have the rest of the lectures?

[@introductiontocryptography4223]

Lecture 24 is in fact the last one in our 2-semester intro sequence to cryptography. (BTW, the course targets mainly first-year students who are in a Bachelor program for IT security.)

[@zomaarwat9]

Congrats to your RUB team et al. for the DROWN research.

[@kavinga77]

Professor Paar, Thank you very much for the most informative lecture series in my academic life. I was wondering about the last 4 lectures in the series, are you planning to upload them or this is it?

[@introductiontocryptography4223]

Sorry, that is the last lecture of our two-semester sequence introduction to cryptography. I will release soon the lecture notes for my advanced class "Implementation of Crypto Algorithms". I am glad the videos are helpful :) cheers, Christof

[@HahuMelody]

Introduction to Cryptography by Christof Paar I have no word how can I explain,,, more than words your toooo smart and the way you take a lecture is special.

[@allardkeeley267]

+Introduction to Cryptography by Christof Paar Does you textbook (which I have ordered) cover the missing lectures? And do your notes on Implementation of Crypto Algorithms requires a knowledge of C or C++? Thank you for a very well presented series. Your cameraman is good, thank goodness.

[@introductiontocryptography4223]

Dear Allard, No, C or C++ is not required for my implementation course. The students are required to do C programming assignments, but that is not really necessary for learning the material. I had planned to video-record the lecture but my sabbatical did not allow this. I hope to do this in early 2017, though. I will release my lecture notes soon. Regards, Christof

[@snitins]

thanks. pls share other 4 lectures if you have done like you mentioned early 2017 :)

[@vaibhavsingh8122]

You are awesome. I like the way you teach and you are also very good at what you are doing. RUB is certainly very lucky to have you and i am very lucky to have this series of lecture. Are there any other content from you,online..? if yes, can i have the links..

[@introductiontocryptography4223]

I am glad the lectures are of help. So are, I do not have plans for other lectures. The lecture notes for my advanced course "Implementation of cryptographic schemes" are online, though. Please check emsec.rub.de/teaching/literature/ regards, christof

[@AjitYadav-sy3dh]

great lectures.. thankyou.

Prof. Christof, are there other available classes online of this course? I mean, other B. Sc IT security classes.

[@nicholastebandekebolitho3856]

thanks for everything is there a way to upload the last four lectures to complete the course

[@introductiontocryptography4223]

for clarification, Lecture 24 is the last one of this two-semester sequence. best, christof

[@abisheikg]

Thanks. Good lecture on certificates. Could have added some info about X.509 and PKI .

[@angeloaraya916]

Proffesor, there will be a second book? it think that in this "Introduction to Cryptography" you cover almost every aspect known acttualy.

[@introductiontocryptography4223]

No, we do not plan another book at the moment. Please note that the lecture notes of my follow-up course "Implementation of Cryptographic Schemes 1" are freely available at: emsec.rub.de/teaching/literature/ regards, christof

[@thinhare]

Both Alice and Bob each has got a pair of keys respectively (a public key and a private key). When Alice sends a message to Bob, she uses Bob's public key for encryption which only Bob who has the private key to decrypt it, the man in the middle Oscar does not have Bob's private key, how does he decrypt the message Alice send for Bob?

[@amanroy8447]

Not all heroes wear capes!

[@roseb2105]

how doe bob verify that the certificate is no coming from Oscar again? also to clarify what was said at the end of the lecture did you mean that Oscar can not really learn about a public key because once the reall key is used it is not needed again ?

[@tabamon97]

Professor Paar, I am taking a class based on your "Understanding Cryptography" textbook. I am following along with you. Unfortunately, I am unable to go over problem 13.12. Does anyone in the comment section of his videos have any suggestions? Looking for any sort of help.

[@roseb2105]

these lectures are great is this the last one?

[@introductiontocryptography4223]

Ja. cheers, christof

[@saadsb6499]

If Oscar sends the Alice certificate with Alice's public Key prentending that he is Alice ,how Bob can know that he is communicating with oscar and not Alice?

[@introductiontocryptography4223]

Good point. In practice, the CA must make sure that only Alice has a valid certificate that is related to "Alice". In practice, that could mean that Alice has to present a government-issued ID card or some other form of identification towards the CA. -- As you can imagine, this is not always easy to implement in the digital space.

[@SauravSingh-uv9fs]

Dear professor , please give me idea for project on cryptography

[@essbeevanhoutte4095]

Thanks -Oscar 🐻‍❄

[@kenichimori8533]

PKI Public key infrastractue.Total 007

[@martovify]

thank you

[@drydessert4198]

Ich habe Bedenken, dass mein Englisch im Eimer ist, wenn ich mir den kompletten Kurs ansehe. Schade, inhaltlich sicher wertvoll.

[@modato97]

Wir können zusammen sprechen, damit Sie Englisch üben und ich mein Deutsch üben.

[@worldofmaths9957]

Is it the last lecture??

[@introductiontocryptography4223]

ja :)

[@worldofmaths9957]

thank you sir

[@ebeibraheem]

a snake... 17:20 ;-)

[@strip789]

thank u very much sir. if u don't mind..can you give me your email id..

[@Electronieks]

Mimt???