What is digital signature?

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A digital signature is equivalent to a handwritten signature in paper, and a digital signature serves three basic purposes. Digital signature is commonly used for software distribution, financial transactions and other cases where it is important to detect forgery. Digital signatures are very popular with e-mail users.

In this video, I will talk about the digital, uses, and the whole process of creating and sending digitally signed document over the Internet.

Keep in mind, digital signature is not about encrypting document, just like paper-based signature.

Playlist: Basic Cryptography

Advanced Cryptography:

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Sunny Classroom

[amosgakwerere]

the entire semester i did not understand this but only 5 min i got it, thank you Sunny

[Ada-hdzp]

Sunny, I just wanted you to know that today I provisionally passed SSCP and I would have not achieved it without your youtube lessons. You are the best teacher any student could hope for!

[mulimotola]

Great explanation! Thank you! I only want to add that the reason we use a hashing algorithm before encrypting a digest, is to make the digital signature small. Because if the plain text message was 10GB in size, then using a hashing algorithm on it creates a small string of only a few bytes. But we if created the digital signature from the entire 10GB text message, then we would have to send 20GB worth of data - 10GB for the original message, and another 10GB for the digital signature used to verify that it was signed by Bob. In case anyone else was wondering why we use a hash algorithm to create a digest, before encrypting it with the private key to create a small digital signature. Remember, if any small change was made to the original message, the digest would be completely different, and that's why we can use this method to decrease the size of the digital signature.

[faiqarif]

Woah my book fails to explain this in 5 pages, what you did in just a few minutes.

[natolgaa]

I can’t believe I didn’t stumble upon your videos earlier while studying for the CISA. Domain 5 has had some difficult concepts to understand and taking even 30 min to watch a few of your videos has finally made concepts click. Thank you so much, you’re a wonderful teacher!

[manishashenoy]

You explain this better than anyone, Sunny. We are so blessed that you are on YouTube. There are ones that talk for 1 hour and don't explain it as well as you have in 5 minutes. Thanks for explaining it so well!!!!

[psoidonym]

Sunny, your explanations are spot on.
In your Public key video, you made clear, that the process starts with the receiver. Here you pointed out, that digital signature and encrypting the message are two distinct things.
I watched a ton of videos to understand those concepts. No one made these differentiations. Hence, they are critical for the understanding.
Thank you very much for your work.

[axionW]

Thank you Sunny! I was preparing myself on your channel for the cryptography exam for my dream job. I got the job and I explained digital signature, hash functions and PKI exactly the way you do on your channel. Thanks to you I had the best written exam among all the participants. Keep doing the great job!

[wandjlaye_godwe]

At 4.20, he debunks one of the digest confusion peoples are running into - a digital signature is NOT used to encrypt application data. Great job Sir!

[Wolcik]

you explain it very well - the logic is sound and easy to follow unlike some people that gets trapped in the technical details before explaining the basic steps

[abuabdulrahman]

I am reading from the book, it took me hour to barely understand, five minutes video goes directly to the point, thanks Sunny!

[mixupcalledkhichri]

today there was my ppt i was very upset how to explain. Then i pray O Allah help me and finally i watch your video . Thanks to my Allah ..
Thanku sunny everything is crystal clear..

[Artificial_Intelligence_AI]

bob and alice using cryptography techniques again!!! they are amazing lol

[tylercgarrison]

interesting that 5 mins in a free video from someone who speaks english as a second language is more helpful than a $500 textbook and a lecture from an expensive institution..
Thanks Sunny, you're awesome

[prar_shah]

After watching tons of videos... finally I was able to understand the concept after watching your video..thanks alot sir

[warrenchen]

You can explain the most complex concepts so that anyone can understand. Thank you very much

[jjceteceto]

Mostly i never comment the videos i see, really worth for watching and got full concept in just 5 mins. Really it's useful

[dannuttle]

It's embarrassing how little I understood about this, and remarkable how clear this video makes the subject. Well done.

[shivakumarshiva]

I have understood a lot.tqsm sir.today I have my exam.it helped me a lot

[VF]

Somewhat simple concept, but hard to understand just by reading textbooks. Thanks for this vid.