Digital Signatures and Digital Certificates

This video explains the purpose of digital signatures and how they work. It begins by reviewing encryption and decryption using an asymmetric pair of keys, and then explains the significance of this when it comes to digital signatures, namely that it doesn’t matter which of the key pair is made public and which is kept private. The video then illustrates the digital signing process. Specifically, the creation of a hash value for the document (also known as a digest) using a hash algorithm such as SHA256 (which was created by the National Security Agency). It shows how document digest is then encrypted using the sender’s private key before being attached to the document. When the document is received, the recipient decrypts the digest using the sender’s public key. The recipient also recalculates the hash. If the hash values match, the recipient can be confident that document has not been tampered with in transit. The role of a certification authority is also covered. A certification authority issues its customer with a special file called a digital certificate which binds their public key to identifying information. This video also mentions the importance of digital signatures which it comes to cryptocurrencies. A cryptocurrency such as Bitcoin requires a secure mechanism for updating its decentralised ledger.

[@ramasif9983]

This is by far the most simple explanation of the presented concepts - in a way that everyone understands it and from then can move on to the more complicated parts. Excellent.

[@kisme01]

this is the only video you need to watch if you want a practical understanding of digital signatures

[@seetsamolapo5600]

Wow! This might be the best video on data integrity and data authentication
- digital signatures rely on asymmetric cryptography.

[@saikrishnasunkam4344]

This is the single best illustration/explanation of this concept on the internet. Keep making these videos man, you've got talent.

[@ComputerScienceLessons]

Thank you :)KD

[@kadircangulde2322]

Such an explanation with downgraded complexity, but with an upgraded realization. Exceptionally wonderful.

[@ComputerScienceLessons]

Thank you :)KD

[@3a1Va1]

Used this video to get my Sec+ a few years back now... Back to refresh myself on this for my SSCP. Awesome video. Thank you so much!

[@ashokantony694]

Studying for CCNA Cyberops , the Cisco documentation on this is a complete mess. This video is pure gold , incredibly simple and clear. Thank you sir , keep up the great work . On more subscriber for your great channel :)

[@zakariyaal2848]

Exactly here for the same reason, good luck on you exam.

[@mostinho7]

Done thanks
0:15 explaining RSA
1:30 digital signatures: it doesn’t matter what key we encrypt with (public or private) the message can only be decrypted with the other key. A message can be digitally signed by encrypting it with the private key and then others can verify the signature by decrypting with public key.
3:58 digital signature example
5:40 sender hashes the message, encrypts the hash with their private key. Receiver decrypts the hash with the sender’s public key, and if it matches the message then receiver knows message came from sender
7:00 why we need digital certificates on top of digital signatures. Someone could be pretending to be the sender, and digitally signs the message. The receiver has no way of verifying the sender’s identity.
Digital certificates is how the receiver can verify that a public key actually belongs to the sender
8:00 how certificate authority works

[@morshedulislamriaad6496]

You deserve an Oscar for that kind of explanation .

[@ComputerScienceLessons]

Thank you. I'll start writing my speech. :)KD

[@redouanelhammouti968]

2 days on the internet trying to understand this subject , your 11 min video made it , thank you alot !

[@ComputerScienceLessons]

Glad to be of service :)KD

[@AliShaikh_744]

I love the narration, the humour, the analogies and the simple and easily understandable format. Thank you!

[@ComputerScienceLessons]

You are most welcome :)KD

[@seetsamolapo5600]

​@@ComputerScienceLessonsthe explanation is phenomenal sir. I wish you could make more videos on cybersecurity topics esp security+. I'd gladly join your patteon

[@billchen4923]

Amazing teaching. After viewing this video, finally I can understand the concept clearly.

[@fromdil6470]

Thank you for simplifying the concept of digital keys and explaining the role of hashing in it. Your explanation has made it easy for anyone to understand these complex theories.

[@ComputerScienceLessons]

You are most welcome :)KD

[@ITTechTips4You]

Perfect! At 6:19 I first thought you made a mistake but after finnishing the whole video you carefully explain how a CA works. Brilliant. Thank you.

[@ComputerScienceLessons]

You are very welcome.

[@soamesphares]

You have talent to explain concepts...Thank you

[@ComputerScienceLessons]

You're very kind. Thanks for the comment. :)KD

[@amir_shayesteh_tabar]

10 from 10! so easy to understand, A good lesson for other CZcamsrs talking about Digital Signature!

[@aaronstones100]

This is by far the best explanation i've ever seen of this. Thanks a lot :D.

[@jyoti9273]

It's crystal clear the way you explain and demonstrate with animation.

[@ComputerScienceLessons]

Thank you :)KD

[@vijayjangid8967]

This channel is underrated!

[@ComputerScienceLessons]

Thank you :)KD

[@romeo98711]

What a brilliant work !

[@gittesilberglarsen1262]

wow! that is very well made. direct, clear and no annoying repetitions

[@ComputerScienceLessons]

Thank you :)KD

[@petercooper3468]

Finally, you explain it crystal clear! Thanks you very much!

[@ComputerScienceLessons]

You're most welcome. Thanks for commenting :)KD

[@ShijenN]

This is the best explanation of digital certificates and digital signature i have come across. Thank you :)

[@ComputerScienceLessons]

Thank you :)KD

[@tanvirkazi6889]

Such a clear explanation - thank you !

[@CzarnaPorz3czka]

thanks a lot for the explanation! I finally I understand all the topics mentioned in the video. Big thanks!

[@navneetiyer]

Thanks for the video. Keep up the good work 👍

[@miraj0072004]

I think I attained Nirvana after watching this!
Thank you!!

[@ComputerScienceLessons]

It's been a while since I've done that for anyone. You are very welcome :)KD

[@kisme01]

i just saw this one video, but this is enough reason to subscribe. whatever you post I'm gonna watch it. damn

[@ComputerScienceLessons]

Welcome aboard :)KD

[@PumpkinJ36]

Finally, thank you so much I've been trying to understand this for a while now.

[@ComputerScienceLessons]

You're most welcome. :)KD

[@Jonathan-dy9ju]

THanks so much for this video, Fought hours to understand this

[@osamaa.h.altameemi5592]

Best explanation ever. Thank you Sir.

[@prabhuyou1]

Excellent!! Explained in such a simple way. Thanks!

[@ComputerScienceLessons]

Thank you too :)KD

[@geoff1121]

finally, someone who puts it clearly and totally

[@ComputerScienceLessons]

Thanks for the comment. Really appreciated. :)KD

[@sadafali4516]

I cannot thank you enogh for this video.
You explained it without extra info
Thanks alot 👍👍👍

[@ComputerScienceLessons]

You welcome. Thanks for the lovely comment. :)KD

[@VictoriaOtunsha]

Thank for this breakdown, it gave me a better understanding of the entire concept.

[@ComputerScienceLessons]

You are most welcome :)KD

[@nguyentrananhnguyen7900]

you took 10 minutes to teach me whatever my teacher trying to teach me in 3 hours, damn !!!

[@ComputerScienceLessons]

Glad to help :)KD

[@yeahright5663]

This is so lucid. Beautifully explained

[@ComputerScienceLessons]

Thank you :)KD

[@vincentadams3807]

This video is really nice! However there is one part I can't wrap my head around. From my understanding:
1: Person A types a message
2: Person A generates a hash of the message using sha
3: Person A encrypts the generated hash using their private key
4: Person A appends the encrypted hash to the message as a signature, and sends it to person B
5: Person B receives the message along with the signature
6: Person B decrypts the signature (encrypted hash) using person A's public key
7: Person B runs sha on the message to generate a hash.
8: Person B compares the resulting hash from the message to the hash from decrypting the signature
9: If they are the same, it;s been verified successfully.
So, what's the point of the sha layer exactly? Why not simply add the message encrypted with person A's private key as a signature? In both cases only person A's public key would be able to decrypt it so I can't see how running it through sha would make a difference.

[@ComputerScienceLessons]

Nice question. One of the key features of a hash algorithm is that it produces a hash value of a fixed size. SHA256 for example will produce a hash value that is always 256 bits long, no matter how big the original message. This ensures that the digital signature is a manageable size, regardless of the document being signed. You might like my series on cryptocurrency which also explains the benefits of hashing.
czcams.com/play/PLTd6ceoshprd7UngbhRHMgKXcWz4PIBEe.html
:)KD

[@cajuncajun183]

exceptionally clear and easy to understand

[@ComputerScienceLessons]

Thank you :)KD

[@rushedhu]

Best video about digital certificates ever.

[@ComputerScienceLessons]

Thank you so much :)KD

[@RaiBilalHaider]

This is best and simplest explanation. Thanks

[@charanpreet2211]

Great Explanation! Much appreciated

[@ComputerScienceLessons]

You're very welcome :)KD

[@marcelorodrigues1683]

Very helpful, thanks a lot !

[@ruibozhang3196]

Very impressive explanation

[@user-bv6bi2sz8r]

Really great video! Explained the things clearly.

[@ComputerScienceLessons]

Delighted to help :)KD

[@naveenchandrakumar480]

Love this video. 100 out of 10 ( ten, yes ), you deciphered it properly.

[@ComputerScienceLessons]

Thank you so much :)KD

[@sabitkondakc9147]

fabulous explanation, simple and clear.

[@ajay7818]

Finally I got this concept!!! Thanks!!

[@ComputerScienceLessons]

Delighted to help - it's actually a brilliantly simple idea isn't it!? :)KD

[@sambo7734]

Thank you for that. The certification authority is the bit missing from most other explanations!

[@ComputerScienceLessons]

You are very welcome. :)KD

[@zamilmastaliyev6967]

great content. I wonder if it calculates different hash for different data so digital signature is changed everytime on certificates or not ?

[@siddharthvishnoi1489]

Thank you very much for clearing the concept

[@ComputerScienceLessons]

You are most welcome :)KD

[@sandhyachowdhary2511]

Great job 👍 amazing explanation 👏 thank you so much .

[@ComputerScienceLessons]

You're very welcome. 😳 :)KD

[@douglaskaicong131]

Wts thats just genius 👏 how people come out with these stuff

[@saadtalani2234]

Amazing explanation. Thanks

[@JossinJax]

Ugh, this is great thank you so much!

[@ComputerScienceLessons]

You're welcome. :)KD

[@WangaRay317]

Thank you so much!!!! This was SOO helpful.

[@ComputerScienceLessons]

You are very welcome :)KD

[@farahnawafleh9460]

That was all I ever needed thank you so much for explaining with that great tone!
You made my day :)

[@ComputerScienceLessons]

Thanks for the complement :)KD

[@abhimanyusinghshekhawat6871]

This is really a great explanation, Question: If we talk about a real scenario, A client browser want to access some webpage and send a request, what would be the actual message first time from client and what will be the revert from the server?
In the example, The message is the actual document but what would be in the actual scenario? is it certificate itself from the web server?, that's what I can guess.

[@VishalKumar-hn7mi]

Thanks for this amazing video, it helped me understand digital signature more better

[@Muwahid999]

Nice way of explaining through graphics....

[@MunyaMazvimba]

simple explanation. all i can say is wow!!!!

[@ComputerScienceLessons]

Thank you :)KD

[@RiyaTheDragonWarrior]

Wonderful video!! Thanks a lot for great explanation

[@ComputerScienceLessons]

You're most welcome. Thanks for the lovely comment. :)KD

[@omarbashir4087]

The research has came to an end

[@hadisoeharto8684]

Very good and clear explanation.

[@Yash-Gaikwad]

Best explanation ever ❤ thanks bro

[@ComputerScienceLessons]

Thank you so much :)KD

[@arminfisher4836]

Good freaking job mate, thanks.

[@ComputerScienceLessons]

TY :)KD

[@shreyashjoshi4188]

Awesome explanation.best video found on this topic

[@ComputerScienceLessons]

Thank you.

[@minefox6071]

Best video on the topic

[@ComputerScienceLessons]

Thank you :)KD

[@ajaxSAF]

Fantastic, thank you

[@adilhassan9443]

This is Gold!

[@ComputerScienceLessons]

Thanks. I appreciate the comment. :)KD

[@pradeepvc1307]

6:44 What is the use of encrypting the hash value here using BOB Private key and sending, As however it can be decrypted by BOB's public key which is available to everyone
You can directly send the hash value or use Gill public key and encrypt and send right?

[@SrRunsis]

Excellent video!!!

[@ComputerScienceLessons]

Thx :) KD

[@blessedzaraz6766]

Excellent lesson!

[@ComputerScienceLessons]

Thank you :)KD

[@tashad200]

outstanding video

[@cebrayiltagiyev2439]

excellent explanation!!!

[@ComputerScienceLessons]

Thanks for saying so. :)KD

[@marcello4258]

so we use the same private key to encrypt data as well as to sign or better use different pairs?

[@rajkirannatarajan9276]

Bob looks like the POTUS 45

[@d.renewood2657]

Best explanation I have seen!😁

[@ComputerScienceLessons]

Thank you :)KD

[@carmellourens3423]

This is Bob, Bob is builder !!! caught me so off guard ahahhaahah

[@ComputerScienceLessons]

He says he's a builder, but he's really a con artist :)KD

[@0xfaizan]

For the past fews months I'm looking for something on cryptography and i found this finally thanks

[@ranapratapsingh3416]

The presentation is really clean.

[@ComputerScienceLessons]

Thank you :)KD

[@defkrogeldiz3197]

Very helpful thanks!

[@ComputerScienceLessons]

You are welcome. :)KD

[@mikespilligan1490]

Lovely work well done.

[@ComputerScienceLessons]

Thank you. Lovin' your name :)KD

[@FabioSouza-jj7oo]

Pretty good, thanks a lot!

[@ComputerScienceLessons]

Thank you :)KD

[@pats.4268]

"This is Bob. Bob's a builder"
Man/Woman of culture, I see.

[@ComputerScienceLessons]

Oh yes. I'm currently in talks wit the Teletubbies. :)KD

[@user-wy9xi6gh9w]

if someone was in the middle of a digital signature between person a and b couldnt they(person m) hash the email/text and sign it with their own key and send that to person b. Then when person b sends an email back to a, person m can hash the email and send a resigned version back to a?

[@just_shim]

Amazing explanation TQ

[@ComputerScienceLessons]

You're most welcome :)KD

[@rumildaolik4905]

Amazing explanation :-)

[@ComputerScienceLessons]

Thank you :)KD

[@raymeiers7949]

Is the Digital Certificate embedded in the document that is being sent or attached to the email message with the document? What prevents a bad guy from obtaining a copy of someone else's digital certificate and using it to pass himself off as the rightful owner of the digital certificate?

[@basees2000]

fantastic channel i love it

[@ComputerScienceLessons]

Thank you. That's music to my ears :)KD

[@tendaijakutindi4175]

Thank you !!!

[@ComputerScienceLessons]

You are most welcome :)KD

[@alksdng97834y]

thank you!

[@evanstayuka381]

Very well explained

[@ComputerScienceLessons]

Thank you :)KD

[@badge2204]

this is the easiest explanation , because the author used the stories and pics.

[@ComputerScienceLessons]

Glad you like my pics.

[@danym-98]

great explanation

[@ComputerScienceLessons]

Thank you. You might like my crypto videos :)KD

[@roasted_guava5706]

If the public key has the algorithm to encrypt a message if someone has the same public key can't he reverse engineer it and decrypt it?

[@m_t_t_]

Does Jill contact the certificate authority to make sure the public key on the certificate (that is sent to her by jack) is the same as the one in the certificate authorities database? If not, surely the digital certificate could just be ‘forged’

[@urssaf343]

the certificate is signed by the CA. if the signature isn't valid it's forged

[@wwolfram33]

@6:12 If How does Jill know that she cannot decrypt Jacks signature with his Public Key? Does the attempted decryption show a 'fail' message or code?

[@ComputerScienceLessons]

This functionality is built into software such as a web browser. Jill will get a message like 'could not logon' or 'transaction failed' depending on what she is trying to do. :)KD

[@wwolfram33]

@@ComputerScienceLessons Thanks, this video was helpful!

[@user-ux1mz9ox6j]

Good Explanation

[@ComputerScienceLessons]

Thank you :)KD

[@mahdidelavaran1099]

thanks it helps a lot

[@ComputerScienceLessons]

You're welcome :)KD