How does public key cryptography work

How does public key cryptography work - Gary explains

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How keys are distributed is vital to any encryption system. Find out how to do it with the Diffie-Hellman key exchange and using public-key cryptography. Find out more: goo.gl/qI6jxZ
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КОМЕНТАРІ: 197

@samueltarley4828 7 років тому

wow this guy is better than my information security professor

@zes3813 3 роки тому

@markod3957 Рік тому

wtf, this had no business being so well explained and suitable for academic consumption. Great job!

@kamalphukan15 3 роки тому

This is, without any doubt, the best explanation video on UKposts on this subject. Thanks a lot.

@ervinlabadero23 5 років тому

At 0:48, the big question is "How does the other party get to know the key?" At 6:15, you said, they both previously agreed on a one-way function. If they are also from different parts of the world and don't know each other, I am now wondering "How does the other party get to know the one-way function?"

@_mickmccarthy 3 роки тому

I realise this comment is a year old, but in case anyone else has the same thought. It doesn't matter if everyone knows what function you're using. As it's a one-way function, you can't figure out the input from the output. In fact, most of these are open source meaning you can go look at the algorithm and inspect it.

@lamensquare 3 роки тому

@@_mickmccarthy Kerchoff principle

@axelfzurital 7 років тому

This video was awesome. I never thought modern encryption worked that way. I really learned a lot from both of your videos.

@SrRunsis 5 років тому

You are an expert explaining! You even took care of the small details that no one explains! Thank you! In 15 min u explained me something i couldnt understand for hours

@matanissler 7 років тому

Thanks to you I understood better how public and private key works! Big shout out to Gray who he keeps working on these technical videos even thought they take a lot of energy to make and they aren't the most popular.

@sikz26300 3 роки тому

Thank you so much! I just spent an hour searching for this example, this is the first video that actually covered the part I wanted to understand, how the data is actually manipulated. Thank you!!

@JimProng 5 років тому

About a year ago I said, this is the best explanation of public key cryptography on the WWW, and I've still not found anything better.

@hrithik5016 7 років тому

I seriously wish my teachers knew as much as you do man!

@ChrisWMF 5 місяців тому

I've seen other videos that explain it but don't explain the part about prime numbers. This is so much better.

@pranavvij 6 років тому

This is one of the best ever videos explaining public key encryption. Thanks a lot!

@brehdem 7 років тому

Good video, I really like the detail you go into. I studied cryptography at uni and all those formulas brought back memories

@hrmfa 7 років тому

Thanks Gary. Much appreciated, even if it's quite complicated. 👍

@Motwera 7 років тому

Quite useful as a summary for some of my ISS classes :p

@JimProng 6 років тому

This is the best explanation of cryptography I've come across. Thanks.

@petermainwaringsx 3 роки тому

Best explanation on this subject ever. I keep coming back for another look, change the numbers for ones I chose, do the math and find it always works. Trouble is, I still don't know for sure how! 😜 Thanks Garry.

@Lazylion572 7 років тому

Love your videos! I have used them several times when writing papers for school. Your videos give an in-depth understanding to the subject. Learned so much from watching your videos though i do wish they were a bit more entertaining since the subject can seem a little um...dry sometimes. Anyways keep up the good work cant wait to watch the next Gary explains!

@bobbybenyard6246 5 років тому

Thank you, Gary. This has helped simplify and explain what could have been a very complicated concept to wrap my head around.

@fersunk 7 років тому

I love this kind of videos... Very informative and easy to understand

@gabrielkotani180 7 років тому

great video, came on the perfect time as I was looking for cryptography. would be awesome to have other videos like this

@1963VLM 2 роки тому

I was searching for 4 days to find such a clear video like yours......!!!! thank you...!!!😊👍

@KartikGajaria 7 років тому

Thank you very much Garry for making the second part. It was really useful... ;)

@rodrigovianna2 7 років тому

Thanks for "part 2". Really great!

@ankithguzz 7 років тому

Very informative. Thank you for making a part two on cryptography. ^_^

@GarySims 7 років тому

I am glad you liked it.

@ankithguzz 7 років тому

+Gary Sims I know it's not really android related, but could you please make a video on blockchain technology used in bitcoin transactions? I think many people don't fully understand how it works. Thanks :)

@Bhatakti_Hawas 7 років тому

Yea a video on bitcoin, how it works etc etc would be nice

@fuzz33594 7 років тому

Prof. Sims - you never disappointed. Thank you.

@mr88cet 5 років тому

Aha! I honestly can’t recall whether I’ve heard the exact, specific mathematics behind RSA before. I knew and/or inferred the general gist of it, but it’s great to see the nuts and bolts spelled out here! Thanks.

@entertainity 3 роки тому

Amazing explanation!. s the document with the detailed explanation still available somewhere? the link in the description unfortunately doesn't work (anymore).

@javierperez2609 2 роки тому

This video is amazing. Thank you so much for your work!

@Anthony-xr6zo 7 років тому

Excellent video. So elegantly explained. Thank you.

@water1051 2 роки тому

Best explanation I have ever found. Thanks so much!

@KushagraJuneja 7 років тому

Faith in learning gets restored when he says, "let me explain"

@davidlawrence8085 3 роки тому

Outstanding on public-key ....thank you much!

@stupossibleify 6 років тому

Excellent explanation. And nice to put a face to Android Authority

@mr.mxyzptlk6233 7 років тому

Had a theoretical math in computer science class in college about 2 years ago. Man that was a lot of fun.

@vuongbinhan 7 років тому

Could you have a dedicated video for hash encoding such as MD5? Btw, this video is great !

@highlander1531 7 років тому

So informative really, but so confusable. Sir you did great job with this video. thanks.

@8982601240 3 роки тому

Thank you for this quality information. Please tell us about token systems as well.

@mariaisabelmartinezcastill4438 4 роки тому

THANK YOU SOO MUCH IT WAS ALL I NEEDED TO COMPLETE MY INTERNAL ASSESMENT ON MATHS

@verkanica 3 роки тому

When he said: "Here comes the magic". It truly was a magic, cause I didn't have clue how he did it!? :) Great Video and the content! It took me 2 attempts to unterstand everything, and when someone asked to explain how Public and private key concept work I was stuck. My answer was: "check it on UKposts, then we can talk about it" Thanks for the video!!!!!!!!!!!

@csbhaskar 7 років тому

I would have given a hundred likes for this! thanks Gary!

@octavianomenezes856 5 років тому

Hi Gary, just one doubt. Try to solve the function could demand a lot of computational power, but taking your example of "H" (72) =13. Someone could use brute force and test a lot of numbers (from 0 to 100) using the public key until find the same encryption result. Someone will not solve the function but will search for the input that gives the same result. In this case, the computational power would be less than necessary to solve the equation?

@sikmann 2 роки тому

Thank you Gary for dumbing it down. Very informative.

@brahimchebli7781 2 роки тому

Daaaamn ,The best explaination i ever seen for RSA , thankss

@Chameleonit 7 років тому

Thanks for refreshing knowledge :)

@aqdhdzwty4132 7 років тому

Gary is the most knowledgeable guy on Android Authority.

@ameyagonal6657 4 роки тому

U r a hero but I suggest u to make seperate videos for seperate encryption methods so rhat we can understand much better...🙏🙏🙏

@MrHotheadalex 5 років тому

😯😯😯😲😲😲 my mind just blew away.......amazing ! N bravo u just explained such a complex concept in just 15 minutes amazing

@ivonsim2522 5 років тому

I like this explanation! it clear my doubt!

@Torterra_ghahhyhiHd Рік тому

Question pls the number e=7 and d=247 are those const? are there some special selections of e and d? dependencia in de message or primer number?

@CharlesVanNoland 6 років тому

There's a mistake on the Diffie Hellman example with the larger numbers that flashes @8:14. Where it says "2087^8001 (mod 7703) = 6265" it should be '6256' like it shows everywhere else :) I had to use my own bigint calculator program I wrote a while back to figure out which number was the correct one.

@NeonWafflez707 6 років тому

Yes I noticed that too! Thanks I’m not alone

@xscorp382 5 років тому

I rarely comment on any video. But this video was just awesome

@tazeemn 4 роки тому

The best explanation ever!

@rohitsamleti4865 5 років тому

Hello Gary, the video is awesome but I have a question regarding DH key exchange...In this video you mentioned two values Y and P to be 7 and 13 respectively...so how Bob and Alice agrees on these same values...?

@pramodchoudhary2136 2 роки тому

any answers?

@xceeder 7 років тому

Hey Gary , I have an idea for a video which I would love you to do , it's about ram management in android I have the oneplus3 with 6gb of ram however the iPhone 7 only has 2 or 3 why or how does the iPhone have so good memory management please enlighten me....

@xceeder 7 років тому

oh damn I didn't read the comments before writing mine I didn't know everyone else was asking you to do a certain subject it's fine if you choose a different subject , it always just makes me wonder how the iPhone is so good with memory , is it an Android/Linux problem and can Android ever get their ram management as good as iPhone maybe I'll never know , I'll still watch your videos no matter the subject you are very clever ....

@xceeder 7 років тому

how do you know that buddy , I always believed it was the ram that they could utilise really well ...

@xceeder 7 років тому

okay thanks for the info buddy....

@MarcoS-bf9tv 7 років тому

Android uses Java which is garbage collected - this means that the runtime will keep pausing after set intervals to clear memory. Java itself needs a much heavier runtime since it uses a virtual machine to execute. iOS uses Objective-C and Swift which do not use garbage collection and has performance similar to C, so the result is more efficiency.

@xceeder 7 років тому

Cool , thanks for replying buddy...

@AAYMF 7 років тому

Excellent work.

@1963VLM 2 роки тому

I think you have a natural talent...!!!👍👍👍👍👍

@micsan381 3 роки тому

Brilliant explanation. 👍👍👍

@francescofreddi4374 2 роки тому

i understand a lot of concepts in only 15 min... after 5 years :)

@bariswheel 2 роки тому

Really great explanation thank you !

@paeyreyes 3 роки тому

Thank you for explaining this!!!

@progtom7585 3 роки тому

this was brilliant, thanks!

@Impostleable 5 років тому

So with the asymmetric encryption it's encrypting the communication from Bob TO Alice, but how does she communicate back securely? Does he give her a public key to talk back to him decrypting the message with his private key?

@johna3909 7 років тому

Great video! Can we please get more of these videos?

@GarySims 7 років тому

There is a playlist!!! ukposts.info/have/v-deo/qp-WjqlknIJezas.html

@AnilBind 6 років тому

Just awesome

@exchange4918 3 роки тому

Good job mate

@thebudkellyfiles 6 років тому

This is excellent. Thanks.

@AB-gd8hn 7 років тому

Referring around 11:52, when Bob wants to send 72, he sends 13 because 72^7 mod 323 = 13. But in addition to 72, there exists another number N such that N^7 mod 323 = 13. So when Bob sends 13 how will Alice know if Bob intended 72 or N ?

@KookoCraft 5 років тому

A B the key determines that

@dinkarchaudhary8858 3 роки тому

Very quick and informative. But considering RSA..... How was the "D" achieved? Thats the link missing.....

@_uditsingh 6 років тому

There's a reason why you use the name alice and bob. I forgot the story behind it. Can you explain???

@petrslavik1215 6 років тому

Because Alice can be shortened as person A and Bob as B

@floordust83 7 років тому

Much kudos to you sir!

@manuelc3671 4 роки тому

Sorry if this question has already been asked, but I'm trying to figure out how to calculate D (12:52), I've tried to use my calculator for it but it tells me that D is 0.142857 and not 247 and I can't figure out why. Any chance someone could help me out? thx

@Dan-tg3gs 3 роки тому

what are some common use cases for this kind of cryptography? Is Diffie-Hellman the most widely used by all encryption applications?

$@refractedphoton$

@refractedphoton 5 років тому

Really good video. Thanks so much.

@techtranslated8218 7 років тому

Wow very informative and interesting!

@Typestyle 7 років тому

The algorithm Y^X(modp) is shared as the public key revealing Y and P's value to all. Supposedly the attacker has private key He also would be able to decode the message since Y and P values are known to him, right??

@howtoandroid7523 7 років тому

So how does the exchange of Y and P work? I mean, if it's a public algorithm you can simply insert the results of Bob and Alice send between each other. If not, Y and P are exchanged unecrypted...

@GarySims 7 років тому

Y and P are public knowledge and it doesn't matter if they are know. There are an infinite set of numbers that result in 4 when plugged into the formula and Eve can’t tell which number it is. For example 7^22 (mod 13) also gives 4.

@Freddy3792 7 років тому

I thought I missed this as well.

@howtoandroid7523 7 років тому

Oooh, I thought they were inserting 4 and 10 as X and not as Y. Thanks for the answer. I should listen more careful next time :D

@GarySims 7 років тому

There is also a written article linked in the description, you might find it useful for reference.

@rianp1300 7 років тому

You posted cryptography videos just when I take cryptography class this semester

@rianp1300 7 років тому

and yes, Alice and Bob does exist

@navjotsingh2251 4 роки тому

Rian P there are two people in my class called Alice and Bob, my lecturer literally gets them to stand up and go to the front for demonstrations. LMAO.

@obsidiansiriusblackheart 6 років тому

About to go write my exam on this stuff lol thanks man

@abdullahmoiz8151 4 роки тому

Very informative thanks a lot

@NevaehBeatez 7 років тому

The public key cryptography part was way too complicated but thanks for trying to help my small mind understand lol

@jonassteinberg3779 5 років тому

Keys are typically 2,048 or now more commonly 4,096 bits, not 248 and 496. He just misspoke, but in case anyone randomly reads this : )

@Sleeping-nomad 6 років тому

Thanks!

@rmsoft 7 років тому

amazing guy, great video.

@ChristianMeyer 7 років тому

Very good video, but one question: Why do both get the 3? What's the mathematical proof for that?

@unknownluck130 7 років тому

just take 10^10 then modulus divide by 13, and you'll get 3

@tejara01 6 місяців тому

@12:04 If I was Eve, I could see a) the agreed formula M^E(MOD N), b) Alice's key ( N - 323), c) the agreed E value (E - 7) and, d) what Bob is sending (13). Therefore I know 2 of 3 "unknowns" and can solve for it. Am I missing something??

@hugohell8290 7 років тому

nicely done 😃

@seddikreghis2589 7 років тому

Hello Gary sims i really like your explains and all ur vids and i was thinking if you could make a video about cicada 3301 have a Nice day :)

@rikenm 6 років тому

I have been searching one question everythwere. Where can d(aka secret key) be stored in android? I saw people saying people can root and just read the key.

@thememace 3 роки тому

since the dynamic shortened link above is broken. Here's the working one: www.androidauthority.com/public-key-cryptography-717863/

@SlayerFoxX 3 роки тому

Great video

@hichamtribak1944 6 років тому

The FunctionY^Y(mod P) must be known only by Alice and Bob?

@pramodchoudhary2136 2 роки тому

How they know it without sharing, and if eve get their hands on this, isn't similar to getting access to keys?

@Jose1maneZ 5 років тому

great video! thanks!

@ryadkr9716 7 років тому

who is the best phone lg g4 or galaxy s6???

@GarySims 7 років тому

And the connection with public key cryptography is?

@navjotsingh2251 4 роки тому

Gary Sims maybe he wants to make sure which phone has a better implementation of security? Lol.

@francoolayat.3731 6 років тому

Nice !

@chaweb1234 5 років тому

You switched the public variables up. The exponent (X) is supposed public not Y

@DeputyDawgAtl 3 роки тому

Ok what i'm still tripping on (Using Alice and Bob in my example) - I get that Bob's public and private key are mathematically linked. However if Alice is across the globe how is her public and private linked to Bob. So as I understand it, Bob will use his public key to encrypt a message and send to Alice which she uses her private key to decrypt. OK i'm fine with that. But how is Alices private key linked to Bobs key? If Bob wants to send another msg, say to Tom - again he uses his public key to encrypt. Tom uses his private to decrypt - how is Tom's key linked? I'm missing something super basic here. Any help appreciated

@nickspirit3 7 років тому

what are the vulnerabilities of public key encryption?

@haydo8373 3 роки тому

Has this been simplified? If a and b are prime numbers and their product is shared, what's preventing someone creating a table of all products with their associated prime factors... All of the prime known numbers are available and storing every derivation of multiplication with other prime numbers alone wouldn't be difficult, product length alone would easily reduce the search in the table.

@highlevelshadinglanguagehl4325 3 роки тому

You go for it, Bud. Millionaire by Christmas!!!!

@haydo8373 3 роки тому

@@highlevelshadinglanguagehl4325 haha, obviously I don't know what I'm talking about

@haydo8373 3 роки тому

@@highlevelshadinglanguagehl4325 Okay so it seems like there are quite a few of them if this person is correct lol "There are very many hundred-digit primes to find. We could cover the Earth in harddisks full of distinct hundred-digit primes to a height of hundreds of meters, without even making a dent in the supply of hundred-digit primes." Or approximately 7.853 x 10^11,185,263 :)