DES -- The Algorithm
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- Опубліковано 14 жов 2013
- DES -- Data Encryption Standard -- has been the workhorse of modern cryptography for many decades. It has never been compromised mathematically (not in the open literature, at least), yet, its design notes were never made public either. Many who use it are unaware of how it works. Here we open the DES box and find inside a repetition of sub-boxes in which very simple primitives are at work: substitution, transposition, split, concatenation, and bit-wise operation. DES inside teaches us that complexity is comprised of a lot of simplicity.
- Наука та технологія
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.
+Michael Maigwa You are very welcome! It's why I post it!
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.
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!!
Precise, easy to follow and just what you need. Thanks a ton for this vid.
Thanks for your precisely definition for the DES Mr.Samid
Just wondering, why were you teaching in a jungle?
yeah hahaha
hahahahahahah I am wondering as well. Encrypting in a jungle
@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. :)
Great, then why don't we disguise our offices like jungles and play some virtual ambient sounds around
HAHAHHAHAHAHHAHAHHAHAHAHAHAHHAHAHAHHAHAHHAHAHA
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.
WoooW exactely what the teacher must be
even without after effect and no other effect soo simple it is soo clear thanks soo much
Thanks a lot for the video, it was very easy to understand the content, this is exactly what i was looking for.
Thank you very much Pro. It was great lecture, very accurate and well define. Great work, Please, carry on.
Thank you so much for such clear illustration
Thank you, this was so easy to understand, DES seemed so scary but you made it so easy. God Bless.
Glad that I could be helpful, bless your heart!
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
Excellent video and easy to follow. Thank you!
Gideon, you are amazing! Thank you very much for publishing those video!
Thanks -- your comment keeps me motivated, stay tuned!
Thanks, will try to add more!
Thanks Sir Samid, this was really easy to understand and quite helpful :)
Absolutely Loved It
Thank youuuuu
This is excellent! I was not able to understand this on my native language, but very quickly understand yours explanation! Thank you!
this video has a great vibe
Awesome to hear you always mr. gideon ,good lecture and trust me its not boring .
Thankyou sir..! your way of explaination is very good..!
A really nice video with awesome explanation.... thank you sir...
Perfect explaination!
thank you Sir! Great Explanation!
Thank you very much!
absolutely great!
thank you dr for the explanation, really helps me :)
I didn't need to know exactly how it worked, just a concept. Thank you this was well explained.
I need help with a question
Excellent, thank you.
thanks!
Fantastic, thank you sir
Well explained and found it very useful
Nicely explained. Thank you sir :) :D
Thank you, very well undestandable
Very well explanation sir, Thanks.
Very well said.
Thank you very much sir, clear and neat :)
thanks a lot for the video.... great explanation sir...
aftr 5 hrs, we have crypto. exam.....& ur concept is gonna help me a lot, i m sure abt that....thanx :)
Thank you so much,this is very clear! :)
Thank you Ceci!
Thank you master!
The initial permutation T is inversed at the end. The proper notation would be T on the power of (-1) on the end permutation.
billion of thanks Sir
+sara Happy to be helpful. I know that so many explanations are only confusing.
Thanks Gideon! well explained,
I would add an explanation of how a decryption process is done in such method.
thank you sir for this awesome and helpful video
Very helpful thank you!😌
PERFECT, PERFECT!
Thank you professor
thank you soo much sir........
Thank you!
really thank you.
Thank You Sir. :)
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
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."
this is awesome. You don't even need to beg for Subscribe and Share like others. You are really good Mr.Proffessor.
Thank you sir.. Very clear... :) Great explanation...
Thank you.
Thx sir awesome tutorial
thank you
super useful for my semester exams
thanks a lot sir
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?
Thank you so so much sir
Glad I could be of help, do good!
saved my semester :D
Nice explaination thank youu
awesome..!!!!
thank u sir,it helped me alott :)
thanks Gideon
Great great work..
WOuld you mind going through DUKPT -derived unique key per transaction
thanx a lot sir ji
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
This is how teaching should be like. Showing what happens before showing mathematics behind it. It slowly creates interest learn to mathematics behind.
You got it Iresh -- math has to follow the story, not the other way around!
Awesome....Sir
thank you for taking the time to say a good word-
Thank you sir
thank you sir, your explanation was great.
You are most welcome, Aymen!
I hope you enjoy the other videos too. The full course in in www.wesecure.net/learn
Awsom explaination ... clap.. clap.. clap...
Thanks!
Obrigado!
The 16 runs are needed to prohibit differential cryptanalysis attacks.
+procletnic 17 rounds would have been more protective... DES design considerations have never been fully exposed, contributing to the various conspiracy theories.
thank u sir that was so helpfull :)
Now that AES is the standard, is DES still useful for some applications? - Like your explanations. - many blessings.
how does DES deal with extra bytes where these bytes couldn't construct a block ??
+Evram Hany padding to complete the last block.
nice explanation Sir, you save my final exam.
way to go!
Lol claps in the end cracked me so badly... Hahaha
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
Can you teach me about TinyDES? and for example.
Thanks a lot!
why were there a clapping sound effect at the end?
best video
great
which is the most secure encryption algorithm in the world?
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 UA-cam video: ua-cam.com/video/j1jnaf6GvJs/v-deo.html ) can be set for any desired security -- up to absolute mathematical security. See details in RandomnessRIsing.com
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.
Sure, Seiidkhan, the entire course and the video, slides, and all is in WeSecure.net/learn. Glad you enjoy it.
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.. 😄
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.
i have to implement des in software using java
sir can u tell me how can i do it
Get this man a marker. btw Thank you so much.
Indeed my students gifted me a box of markers... Compare to all the shiny presentations, old school still works best!
Hello sir .. I would like to get your help to understand the MD5 work ..
Hey Gideon,
Isn't the key 64bits (with 8 bit parity), so the actual key length is 56 bits, rather than 48?
+Ben Forrest actually, i was wrong. 48 bits per round (different each time) , from the 56 bit key.
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.
Thank you :)! - Your neighbour from Palestine
tnks well explaination but need some how deep sir its not that much short but thnk u so so much
Ok... Now i need Feistel ;-)
You cannot define The Algorithm. It defines you. It's instructs you.
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??
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.