DES -- The Algorithm

[@michaelmkangethe]

As an Information Security Practitioner, Enthusiast and postgrad Student I would like to thank you for your clear and well elaborated description of DES, and ALL other VIDEOs you have made.

[@GideonTheTeacher]

+Michael Maigwa You are very welcome! It's why I post it!

[@ryanwwest]

For more info on why 16 rounds are used, "the reason that DES uses 16 rounds appears to be because differential cryptanalysis is more efficient than exhaustive search until 16 rounds are used". In simplified terms, it would be easier to mathematically determine the key than brute-force the algorithm with all possible key combinations, until the algorithm uses 16 rounds, at which point brute-forcing it becomes more efficient.

[@kalalakalonji8454]

Hi Dear Professor , Thank you so much for your clear explanation. You have the power to make things simple and clear. I wish you all the best. May the Universe be with you!!

[@john_smith29125]

Just wondering, why were you teaching in a jungle?

[@Darkness93]

yeah hahaha

[@nikolu9560]

hahahahahahah I am wondering as well. Encrypting in a jungle

[@SHRIANSHPANDEY]

@seantay1999 thats because of the proven fact that when you learn something around the nature like trees , birds and etc. Then your brain understands the things much more faster and easier unlike inside any of the building. :)

[@nikolu9560]

Great, then why don't we disguise our offices like jungles and play some virtual ambient sounds around

[@TpZReverse]

HAHAHHAHAHAHHAHAHHAHAHAHAHAHHAHAHAHHAHAHHAHAHA

[@DilankaMadhawa]

It is very useful and clear to understand. I got a good idea how it works. Specially it was very hard to find a good video to understand DES, but because of your video, I got a good idea. Thanks again.

[@anaibrahim4361]

WoooW exactely what the teacher must be even without after effect and no other effect soo simple it is soo clear thanks soo much

[@ahmedkeejab2467]

Thanks for your precisely definition for the DES Mr.Samid

[@MrLucasOFF]

Gideon, you are amazing! Thank you very much for publishing those video!

[@GideonTheTeacher]

Thanks -- your comment keeps me motivated, stay tuned!

[@GideonTheTeacher]

Thanks, will try to add more!

[@ShanaSephora]

Thank you, this was so easy to understand, DES seemed so scary but you made it so easy. God Bless.

[@GideonTheTeacher]

Glad that I could be helpful, bless your heart!

[@bluesinmahblood]

Precise, easy to follow and just what you need. Thanks a ton for this vid.

[@flatl1n3]

I didn't need to know exactly how it worked, just a concept. Thank you this was well explained.

[@ricalbelizaire6970]

I need help with a question

[@Ira_11]

Awesome to hear you always mr. gideon ,good lecture and trust me its not boring .

[@regis7374022]

This is excellent! I was not able to understand this on my native language, but very quickly understand yours explanation! Thank you!

[@therealaverma]

this video has a great vibe

[@nimeshdilshan4917]

Thanks a lot for the video, it was very easy to understand the content, this is exactly what i was looking for.

[@procletnic]

The initial permutation T is inversed at the end. The proper notation would be T on the power of (-1) on the end permutation.

[@solangelgonzalez2822]

Great video sir! This gave me a broad idea of des enough to start studying. It did not go super in depth but It taught me something. Thank you

[@RoushanJ]

aftr 5 hrs, we have crypto. exam.....& ur concept is gonna help me a lot, i m sure abt that....thanx :)

[@IreshDissanayakaM]

This is how teaching should be like. Showing what happens before showing mathematics behind it. It slowly creates interest learn to mathematics behind.

[@GideonTheTeacher]

You got it Iresh -- math has to follow the story, not the other way around!

[@merajkhalidkhan]

Thank you very much Pro. It was great lecture, very accurate and well define. Great work, Please, carry on.

[@kaustubhkargutkar8836]

Thank you so much for such clear illustration

[@valentinduchampdechastaign6734]

How do we have 48 bits of plaintext in the subbox while there are 64 bits in the beggining? I don't understand what kind of operation is manipulate here

[@republic8360]

Hey team, Jimmy answered this below: "If anyone is wondering, look up feistel network. The left and right channel are 32 bit each making 64 bit input and then the right channel is expanded from 32 bit to 48 bit so it can be xor-red with the 48 bit round key and so forth and it goes through sbox and pbox to get back at 32bit and at then end you still get the left and right channel of 64 bit total."

[@dafuqiswithyoupeople]

Thanks Sir Samid, this was really easy to understand and quite helpful :)

[@benitorodriguez9714]

Excellent video and easy to follow. Thank you!

[@labib3974]

this is awesome. You don't even need to beg for Subscribe and Share like others. You are really good Mr.Proffessor.

[@procletnic]

The 16 runs are needed to prohibit differential cryptanalysis attacks.

[@GideonTheTeacher]

+procletnic 17 rounds would have been more protective... DES design considerations have never been fully exposed, contributing to the various conspiracy theories.

[@tamirsagi4544]

Thanks Gideon! well explained, I would add an explanation of how a decryption process is done in such method.

[@puspendumatilal6460]

A really nice video with awesome explanation.... thank you sir...

[@Abylash]

Thankyou sir..! your way of explaination is very good..!

[@mayowaibitola890]

Absolutely Loved It Thank youuuuu

[@kieranmcnamara2353]

When the ciphertext reaches the decryption 'box' on the receiving end, how does it know what transposition was used when encrypting the message so that in can it can decrypt the message correctly. Do they all just have a standard transposition algorithm?

[@abhijeetnarvekar]

thank you Sir! Great Explanation!

[@farooqrana7205]

Write a detailed note on the Design rationale of Data Encryption Standard with a focus on the design of S-boxes. if u have then plz share a link

[@nuhailya]

thank you dr for the explanation, really helps me :)

[@user-um7tw6kx4r6]

Fantastic, thank you sir

[@shafrahijaz4548]

Well explained and found it very useful

[@denismwiti]

Great great work.. WOuld you mind going through DUKPT -derived unique key per transaction

[@jcpartri]

Now that AES is the standard, is DES still useful for some applications? - Like your explanations. - many blessings.

[@Gigolas88]

Lol claps in the end cracked me so badly... Hahaha

[@omarathon5922]

Excellent, thank you.

[@GideonTheTeacher]

thanks!

[@dulevw]

Perfect explaination!

[@evramhany6368]

how does DES deal with extra bytes where these bytes couldn't construct a block ??

[@GideonTheTeacher]

+Evram Hany padding to complete the last block.

[@Shrishification]

absolutely great!

[@volkerschmidt5190]

Verry interesting !! Question: If I understand this right,what gives DES its security against decoding(Eve is klistening in) its the central part of DES. The two transposition in front and at end give only some sort of security,if the method of the 2 transpostions is not known. This obviously is the principle os security by obscurity. This leads me to another question: How much of DES is already known (publicly) ? If the principle of the 2 transpostions is already openly known,there seems to bne no security in using them?! ..sorry for my english-not a native speaker-actually from Germany-typos as well I suppose

[@salmanraza5223]

Very well explanation sir, Thanks.

[@balaramkantipudi3728]

super useful for my semester exams

[@seiidkhandzhursumbekov1013]

Hello Professor! You said about slides. What slides do you mean, and where they are located? what site? please could you give me a link to the slides? thanks.

[@GideonTheTeacher]

Sure, Seiidkhan, the entire course and the video, slides, and all is in WeSecure.net/learn. Glad you enjoy it.

[@desarrollofacultaddeingeni7137]

Thank you, very well undestandable

[@jean1551]

Thank you very much!

[@oscar43211234]

which is the most secure encryption algorithm in the world?

[@GideonTheTeacher]

Intractability based algorithms like DES, AES, RSA, etc. are only secure against an adversary who is limited by the same mathematical insight of the cipher designer. By contrast randomness based ciphers like old Vernam or the new Bit Flip Cipher ( check out this KZbin video: kzbin.info/www/bejne/oGLNn5Sca6ypgNU ) can be set for any desired security -- up to absolute mathematical security. See details in RandomnessRIsing.com

[@pramithasdhakal5367]

thanks a lot for the video.... great explanation sir...

[@aminsmth]

Thank you very much sir, clear and neat :)

[@captaincqy]

5:26 Something's wrong with my... (takes a while to think)... pencils. XD

[@garthmoil3733]

You cannot define The Algorithm. It defines you. It's instructs you.

[@Sara-mg9eo]

billion of thanks Sir

[@GideonTheTeacher]

+sara Happy to be helpful. I know that so many explanations are only confusing.

[@yahyaabdullah5141]

thank you sir for this awesome and helpful video

[@AbhishekPandey-hf5qs]

i have to implement des in software using java sir can u tell me how can i do it

[@manishasharma-pi7ge]

Nicely explained. Thank you sir :) :D

[@greenshine82]

Thanks a lot, maybe it's used 16 stages because if its used less, then its need less time to break it in brute force. I don't know, what do you see sir.

[@ammu000005]

Awsom explaination ... clap.. clap.. clap...

[@GideonTheTeacher]

Thanks!

[@hendy7933]

Why 16 rounds? In my opinion, it because of the Internal Key generation which is the internal key will generate by moving to left 1 or 2 bits (Mostly 2 Bits) that means if it already move 16 round (16 x 2 Bits ~ mostly), the key will place like the first key. I think IBM create it 16 round to make the DES more securable.. 😄

[@fasial3]

nice explanation Sir, you save my final exam.

[@GideonTheTeacher]

way to go!

[@ranj234]

why were there a clapping sound effect at the end?

[@haqeealkhaleed6115]

Hello sir .. I would like to get your help to understand the MD5 work ..

[@elpidiopiscosiii6435]

Very well said.

[@jimmy000]

I dont understand how 64 bit goes in, gets mixed with 16 round of 46 bits key and then outcomes a 64 bit, what about the rest of the 18bits??

[@jimmy000]

nvm I got it. If anyone is wondering, look up feistel network. The left and right channel are 32 bit each making 64 bit input and then the right channel is expanded from 32 bit to 48 bit so it can be xor-red with the 48 bit round key and so forth and it goes through sbox and pbox to get back at 32bit and at then end you still get the left and right channel of 64 bit total.

[@cecizucchino3413]

Thank you so much,this is very clear! :)

[@GideonTheTeacher]

Thank you Ceci!

[@Sri_Hari_527]

Awesome....Sir

[@GideonTheTeacher]

thank you for taking the time to say a good word-

[@pasindujayaweera5575]

Thank you master!

[@gunarajesh1]

Thank you sir.. Very clear... :) Great explanation...

[@TungNguyen-kc7jz]

Can you teach me about TinyDES? and for example. Thanks a lot!

[@temesgenayana7610]

Thank you professor

[@cj5925]

Get this man a marker. btw Thank you so much.

[@GideonTheTeacher]

Indeed my students gifted me a box of markers... Compare to all the shiny presentations, old school still works best!

[@ForrestBlazininnit2k]

Hey Gideon, Isn't the key 64bits (with 8 bit parity), so the actual key length is 56 bits, rather than 48?

[@ForrestBlazininnit2k]

+Ben Forrest actually, i was wrong. 48 bits per round (different each time) , from the 56 bit key.

[@9730196520]

Sir how to encrypt the character (ABC) or (ABBC) ? can u clear my doubt sir.!

[@AymenAlBaili]

thank you sir, your explanation was great.

[@GideonTheTeacher]

You are most welcome, Aymen! I hope you enjoy the other videos too. The full course in in www.wesecure.net/learn

[@Keepkip]

PERFECT, PERFECT!

[@sanderverweij]

The best way to keep a message is to have no massage

[@radalgo]

thats all well but then hw do u communicate?

[@sanderverweij]

I have to think about that ;)

[@normanpilusa554]

Started very well but explaining the rounds would have been better with the aid of a block diagram like you did with the other modules.

[@Kekir]

really thank you.

[@gvsagar6085]

thank you soo much sir........

[@VivekRaghavs]

Thx sir awesome tutorial

[@durgeshrai2132]

Thank You Sir. :)

[@-mafeni-3758]

thanks Gideon

[@seyyidahmedlahmer1166]

Nice explaination thank youu

[@SravaniVadlamani]

Thank you.

[@poyaclans6302]

Thank you so so much sir

[@GideonTheTeacher]

Glad I could be of help, do good!

[@ТимурГалимов-л5ю]

what happend with another 16 bits ?

[@russiactu2011]

Thank you!

[@amiteshkumar3057]

thanx a lot sir ji

[@bibhurajsinha1522]

saved my semester :D

[@rohitpatil7836]

thank u sir,it helped me alott :)

[@fb767]

Thank you :)! - Your neighbour from Palestine

[@ratkak]

thanks a lot sir

[@TheKhan9191]

tnks well explaination but need some how deep sir its not that much short but thnk u so so much

[@anuragdeep9221]

thank you sir

[@cronexcool8809]

976A5A14463A3055 ISSO E UMA CRIPTOGRFIA DES ? E COMO VER OS 16 DIGITOS REAIS DELE ALGUEM SABE?

[@muhammadnajat3621]

thank you

[@shubhamsengar1883]

Thank you sir

[@jamalghatit]

Obrigado!