Playfair Cipher

An explanation with examples of how to encode and decode messages with the Playfair Cipher.

[@Henchetarian]

Not my first video to try to understand this, but my last - awesome explanation! thank you!

[@NovaAnimations]

I feel smart now.

[@afanofthem2734]

First I thought 20 min, that's long. I ended up enjoying every second of it. Thank you!

[@matxzx]

Omg thanks for this explanation! I'm following a course at university and they recommended us a book to read wich explains the Playfair Cipher in the most horrible unclear way... This is so much clearer! I'm putting this video in my bookmarks! Thanks again

[@videosbykevin2938]

You are very welcome, Mathieu. I'm glad I could help.

[@andreasorourke4252]

lol i'm reading the same book. It uses complicated equations that make it so much more difficult to understand

[@saurabhprabhakar6890]

I can't believe myself!! You just tought me a NEW unique language in just 19 minutes video. Love your knowledge and the simplest way you explained it. Just WOW.... Please accept my gratitude... God bless you sir 🙌 👍

[@emmachristopherson8907]

🏅 First time I've ever commented on a video. This is THE best explanation video hands down. Thank you!

[@videosbykevin2938]

Thank you, Emma. I am genuinely honored.

[@humairasher2000]

@@videosbykevin2938 sir how to decrypt a message if pair is identical (consist of same letter)

[@thehaigu321]

@@humairasher2000 I believe in this case you'd want to replace the second occurance of a repeated letter with a sort of placeholder, such as X or Z, that way all pairs of letters are unique

[@humairasher2000]

@@thehaigu321 thanks

[@thehaigu321]

@@humairasher2000 no prob mate

[@CataRaen42]

Who is here watching just for fun and not for school or anything?

[@carlos1004Alvarez]

Yane Lane yeah just finished watching National treasure 😂

[@antipusrises]

I’m trying to figure out a clue in a book I’m reading all by myself 😅

[@uschurch]

I'm watching this out of interest. I just had to study some cryptography for school but now I'm interested in learning more!

[@Nomadgammer]

Definitely

[@zt3853]

Kevin: MEETMEATNOON = Meet me at noon me: meet meat noon

[@jjpxggy9101]

ZTAso Lol, so relatable Hehe, Food lovers ❤️

[@ne_wi911response8]

I got MEET MEAT NO ON

[@geo.33]

😂

[@RabbitTheKing]

Same

[@jamessmith8727]

No Kevin it is meat me at noon, not meet. lol

[@CJ_DJ]

They mentioned the play fair cipher in National Treasure 2, so I was curious what it was and so I came to this video. Really good job! I loved how detailed you were with it. I will definitely be using this to send secret messages to my friends.

[@athomeescaperooms5696]

This was an incredible and thorough explanation - thank you! I feel like I could now teach others about this cipher based solely on your explanation. Great job!

[@rkx9868]

Literally saved me soo much time, I’ve wrote a whole assignment using the information provided and made my own examples whilst following yours!

[@silverdotmanee]

I was trying to play the game cryptogram but I didn't understand how to play it so came on yt for help but instead of writing cryptogram I wrote cryptography and found myself here and I have apparently learned how to code and decode playfair cipher now... Boy the way you were able to explain to someone who knew nothing about it and yet they managed to learn. You got a special talent! You were funny too so it wasn't even boring 💜👏🤗

[@IamAhmedMohammed]

He is super calm 😂❤ That's help the understanding process in the brain meats 😂❤ This will help me pass my exam tomorrow, god bless you so very much teacher ❤

[@anooshfatima3001]

What do you study

[@IamAhmedMohammed]

@@anooshfatima3001 Computer science

[@rejuvenatedeyes4786]

Are u done

[@anythingajag]

Brilliantly explained, well done. Just watched National Treasure 2 for the umteanth time and understood the code!!

[@bloodeyhell7026]

Wow thanks for this.. some people did videos on this yet unable to explain or demonstrate. You are a good teacher. i understood it flawlessly. i would be glad if you can upload RSA, DIFFE HELLMAN, HMAC, DES, AES AND TRIPLE DES algorithms. then i know for sure i have passed my exams. Thanks once again you are a life saver. already subscribed!

[@maxispeeltspellen4892]

You know a triple des video would be like 8 hours long to explain

[@thegreatkris24]

finally! someone on youtube that knows how to explain stuff ! thanks

[@venkatavula]

That's a very good explanation i have been searching for understanding this topic. Thanks a lot Buddy

[@videosbykevin2938]

You are most welcome, 5H13LD 5P1KY.

[@aniketdeshmane6569]

You r grt , your explaination is lit! Please make more videos

[@dragonblade5370]

Best video I've watched, Easy to understand thank to you!

[@east4081]

Youve literally saved my semesterrrr..God Blesss you

[@Shuck99]

You are a phenomenal teacher

[@XXTheMoleXX]

Very nice. Thank you for the upload.

[@ashleypursell9702]

great video with simple explanation, thanks so much!

[@videosbykevin2938]

You're very welcome!

[@Metrious]

"Uncopyrightable" and "dermatoglyphics" are two of the longest words that don't repeat a letter. Great keywords.

[@vedran3775]

Antidisestablishmenterianism

[@Metrious]

@@vedran3775 yes that is the longest word, but it has repeated letters. The two I noted above have no repeated letters.

[@billjoe5991]

@@Metrious yeah but you could just not write down the repeated letters when making the grid. So if the word has for example two A’s you could just write the word the way it is but leave out the second a

[@Metrious]

@@billjoe5991 Whereas you are correct it is easier to remember with no repeated letters. Otherwise you have to remember how you spelled it without the repeated letters. Other than that you are perfectly correct.

[@user-ou3kl3ed1v]

I owe you big time

[@videosbykevin2938]

You're quite welcome. Thank you for watching.

[@animepabu5526]

Everyone’s saying what a great video (totally true) but I’m over here just watching him write with that nice hand writhing. It looks like a typing font

[@renatorodrigues1500]

Thank you so much for your explanation !! I love to make this things !!! 😎👌 I'm from Brazil !!

[@dunkelheit8594]

Thanks for the video! This is gonna help me a lot.

[@muhamadhaydar8419]

Saved my time, thanks Great explanation 💖❤️

[@deeptivaze4383]

Very well explained, thank you.

[@rahxephonmanga9802]

My new favorite cipher.

[@paulinatruck5316]

Maybe I missed the explanation but what if you need the letter that you are skipping? In this example it was the “J”. Would you use the “X”?

[@sengyongtan2317]

Thanks alot......It really help me to do mine school project

[@neOnPinguinlps]

Thank you so much! I really need that for school but there was no German speaking video. Great job :)

[@videosbykevin2938]

Bitte schön. Danke fürs Zuschauen.

[@kichq248]

You deserve a subscribe,Thank you so much man!!!

[@videosbykevin2938]

You're most welcome, kichq. Thank you for watching.

[@sinisterblades7609]

This is so fun damn i started this class at the uni and iam so hyped to learn all of this

[@ranaai9990]

Such good explanation 💯

[@youtellme_studios4330]

does he explain the "back up" thingy in the code he gave us? because i rewatched the first 10 minutes twice and i never heard such thing

[@walidhouse]

can we use numbers grid to code message?

[@The_Shank]

Great explanation!

[@lauzia6098]

this is really helpful thank you so much

[@SomeBrainiacRBLX]

What if there is an alone x at the end? I'm trying to encode "Orange Box" But have a leftover x at the end.

[@karinemiranda3551]

Great explanation! Helped me a lot! Thank you! ;)

[@videosbykevin2938]

You are most welcome. Thank you for watching.

[@NoteyouraveRage]

Wow! very helpful.

[@FayettiSiqueira]

If you add the numbers you can use all letters and numbers in a 6x6 table. With the bennefit of encoding numbers as well

[@jeffreyweaver9854]

Check out Martin Gardner's book "Codes, Ciphers, And Secret Writing" for his version of the Playfair Cipher, which does use a grid of randomly placed letters and digits!

[@celineguler]

I love your channel sir

[@adrian7796]

Awezome Explanation !! =)

[@AaronToponce]

This is a phenomenal video, as are your 2 paper Enigma videos. However, I want to mention a couple things when using the Playfair cipher. First when keying the Playfair cipher, you really should use an RNG to scramble the 5x5 grid. The threat model is an adversary that knows you're just using key words to key the Playfair cipher, and as such, writes a computer program to brute force search 5x5 grids based on simple key words. However there are 25 unique letters in Playfair, which means there are 25! (25 factorial) possible grids. In terms of computer security, this is about 83.68 bits of security (2^83.68 ~= 25!). 83 bits is robust enough to prevent an adversary from doing a successful brute force search. Second, no two messages should ever be encrypted with the same 5x5 grid. As a mathematician, you should be able to appreciate the mathematics behind using two ciphertexts encrypted with the same symmetric key, do determine the key itself, and as such, decrypt future ciphertexts. Every Playfair key should be ephemeral. This is why code books handed out in WWI and WWII. Field agents would encrypt the message with a key out of the code book, then destroy the key. This isn't unique to one-time pads either. It's the case in modern cryptography with AES, was the case with the German Enigma, and should be the case with any symmetric cipher design. A code book for a 5x5 Playfair grid could look something like: 1. BIUXZGOHERAWLYPDVQTMCKNSF 2. YDISTKQPUXZFCRHVGLOEBMWNA 3. ZAQCVTYOWBEHMDISRPKUXFLNG 4. GSEFXVQTHLPWKUMRYDNZIBACO 5. CEPGIRKLAZXFQBOSWDTYNUHVM 6. BWKSHOTZNYIMRGUCEDFLPQAXV 7. XWBFGTRMUDKCLOEVQASYHPNIZ 8. KYZCLETDXBOVWGAIHFURQSPMN 9. SFMLTKONVCPYXIBWHZEAQUDRG 10. FXNWMOEPDVBQCGSLYHTKAURIZ Two field agents would have identical code books. The person encrypting the message would use key 1, then destroy the key. Next time they wish to encrypt a message, they would use key 2, then destroy that key, etc. Write the grid out left-to-right, five characters at a time, and you have your Playfair grid.

[@animepabu5526]

Very informative thank you :)

[@MarkiMew]

Sometimes people just use code words then go alphabetically e.g. CODEABFGHIKLMNPQRSTUVWXYZ

[@adamnordskog1231]

SOR”TI”E THE MEN OF GUNNERSIDE COULD BE PRAYING WITH DYNAMITE

[@adamnordskog1231]

Page1-100-C • ANDRAE NORDSKOG “the frauds has my grandfathers original Boulder Dam in the Light of the Owens Valley Fraud. ©️2022 by Adam Nordskog”

[@adamnordskog1231]

It says to go with V0C. #1

[@nihil_0x]

What if i add 4 imaginary meaningless character or numbers and make it 6x6, to solve the missing character problem.. I think it should work! 🤔 what do you think?

[@shoetanphilip6050]

Best explanation ever

[@jonathanpascual5353]

Thank you so much! I was able to decrypt the code from the beginning of National Treasure: Book of Secrets just for fun. Also, I've heard of people having the letter 'J' occupy the same square as 'I' instead of fully omitting it , do you think that's acceptable?

[@videosbykevin2938]

You're quite welcome. I'm delighted you found it useful. Certainly you could do that, but I don't think you will find it unnecessary. No one would mistake ionathan, ianuary, or iuniper for anything other than Jonathan, January, of Juniper

[@svenkatasaikumar6698]

Good one dude.. Well said ❤

[@anthonygitonga4526]

What if you have a key word that has similar letters? (Example)

[@winson54]

Good Explaination!!

[@MrVishalarwade]

Thank you soooooooo much 🙏

[@yogokhan7108]

THANKS MAN! LOVE U!!!!!!!!!!

[@notquitehim]

wouldn't it be clever to use the letter you skipped in the grid and use it for double letters, or strings that end with a single letter?

[@heavyglassglass]

but it's not on the grid so you don't have a letter to swap it with

[@karlvonpackal1402]

Sometimes you go clockwise and other times you go counterclockwise when doing boxes (is it simply back and forth between the two every time you come across it?).

[@videosbykevin2938]

Greetings Carl, No, you go clockwise when you are encoding, counter clockwise when you decode. Thank for watching.

[@Stargirl2urStarboy]

What if you had a word with a j? Would u put for e.g. x?

[@cazterk]

thanks very much well explained

[@mikkodarobloxian6316]

I love ur vids

[@geethchadalawada6055]

What if the letter I skipped occurs in my text? Suppose that I was using the second grid you explained with and I want to encrypt January. So what will be the substitution for J? We don't have J in the grid. So what shall we replace it with? Or shall we just leave it as J?

[@videosbykevin2938]

Greetings Geeth, Typically one would use i; no one would mistake ianuary for anything other than January. Also, presumably the receiver of your coded message would be aware of the particular limitation with the letter J and decode accordingly. I might also recommend skipping Q and encode qu as kw if needed: kwit, kwiet, kwalify, etc. Thank you for watching, Kevin

[@twanyajoseph4391]

what happens if you have to use the missing letter do u include it ?

[@009Fahim]

The letters I and J can be counted as the same so instead of writing I in the box we write I/J

[@NothingMaster]

The Playfair cipher is one of the easiest to break.

[@San-li9ml]

Hello good sir, I was wondering if I got this correct, I was doing the thing you did with lizard but instead used the word zodiac and removed the letter k, and for the balloon I used Y an example being LY OY NY. So what I got for doing that was GO NW AV MX I was wondering if I was correct on this or do I need to do it again

[@videosbykevin2938]

Good day Sansaboy, It looks like you've got a good handle on it, but if I understood your description right, I get GO NW AV TA. The last two letters, NY, are both in the fifth vertical column, so encode them using the letters directly below them. N goes to T and Y wraps around to the top to become A. Hope that helps. Do let me know if I have misunderstood your question in any way. Thank you for watching, Kevin

[@apotheoic8865]

I love ciphers and codes, but I have no use for them... non of my friends are into them... can someone suggest a use? I want to use them for fun, but where do I start?

[@Fanahim]

Apotheoic you can make a puzzle type event and find a online community that is into codes

[@larich370]

Thank you sir!!!!!!!!!!!!!!!!!!!!!!!!!

[@lunalikemoon8541]

What abut words with J?

[@samykhouazem1180]

what if we have double xx ?

[@lukab8963]

Pretty sure this is a bit wrong but it just may be another version of the playfair cipher, however the way i learned is that you divide balloon into ba lx lo on not replacing letters just adding an x

[@angelazubal9341]

Does anyone have experience with a 16x16 Fairplay by chance

[@zrve2]

Thank you very much 😍

[@exoticcats6119]

Thanks needed this for school.

[@animepabu5526]

I like your profile picture lol

[@exoticcats6119]

AnimePabu Thanks I like yours

[@MrMack-ex6db]

What do you do if you need to use the letter you didnt include?

[@probnotking]

Skip a different letter! Unless you’re using a palindrome-

[@civilvolcano4492]

What would happen I you put all the letters (in the grid ) in a random order ?

[@videosbykevin2938]

That would be perfectly fine as long as your recipient knows what order you used.

[@alyadel6172]

I have a question.. Could MY in the first example be WO instead of OW?

[@videosbykevin2938]

Hello Aly, Technically, no. It is understood that we always work horizontally in boxes, so M would map to O and Y would map to W, and when deciphering, O would map back to M and W back to Y. That being said, of course you and your fellow code writers could agree beforehand that you will work vertically in boxes, but the Playfair code as designed works horizontally.

[@alyadel6172]

@@videosbykevin2938 Ok thank you so much

[@terrydaniels2998]

so good would fly to the moon for this

[@nadiakacem24]

thank you so much

[@kaivanmehta5771]

If the encrypted message is a sentence.. then how can a space be identified at decryption side?

[@videosbykevin2938]

Greetings Kaivan, Typically one does not include spaces in the encrypted message in order to make any attempts at unauthorized decryption more difficult. However, if you needed a space, you and the recipient would agree beforehand on a letter, usually X, to represent a space.

[@deathcaesar1035]

You're so underrated.

[@noone_8402]

what to do if you encouter the letter you skipped

[@abdelrahmanmaged7131]

Thaaaaaanks really helped

[@gglyt8882]

Very interesting !

[@lisahorgan8183]

Can I ask you question? Can I find another languages the this code ? For example :in turkish

[@videosbykevin2938]

Greetings Lisa, I don't see why not. Because the Turkish alphabet contains 29 letters, I would suggest using a 7 x 4 grid and leaving off a little-used letter as I did here in choosing to leave off J.

[@jyothish99]

Thank you !

[@wwredgrl1515]

Man oh man. This is some John Nash shit. Beautiful Mind.

[@blink6280]

how will you decode word containing the letter you discarded? in your case any word with J in it

[@videosbykevin2938]

Greetings Blink, Typically one would use i; no one would mistake ianuary for anything other than January. Also, presumably the receiver of your coded message would be aware of the particular limitation with the letter J and decode accordingly. One could also skip Q instead and encode qu as kw if needed: kwit, kwiet, kwalify, etc. Thank you for watching, Kevin

[@blink6280]

@@videosbykevin2938 thanks tilte....dep3

[@b5mrjacob373]

appreciate it man

[@thelight9865]

Why should we skip J? My name is Suraj how could I write the letter J? Please answer me

[@joe-wl3qk]

thx for the cipher

[@franksinclair544]

Can you have a code word like Tibia? Or does it have to be single letters that don't repeat

[@videosbykevin2938]

Hi Frank, It must be a word that contains no repeated letters, PENCIL, BIRTHDAY, etc.

[@grzegorzbrzeczyszczykiewic279]

@@videosbykevin2938 You actually CAN use double letter words like BEEKEEPER, but you skip the letters, so the alphabet starts with B E K P R A C D...

[@tarikabaraka2251]

El cifrado de Playfair es un método manual de criptografía simétrica por medio de sustitución. El sistema de cifrado toma pares de letras, o digramas, y las cambia mediante una tabla generada por una clave.​

[@sadmilkin]

Im a little confused on the direction of the square. How come for " ME" you went clockwise and for "ET" you went counterclockwise?

[@videosbykevin2938]

Greetings sad milk, Don't think of it as going clockwise or counter-clockwise. When two letters appear on the corners of a box, encode them with the letters opposite the corners horizontally. Always move horizontally either left or right. Does that make sense? Kevin

[@jack00004]

@@videosbykevin2938 yes it makes more sense... so going clockwise or counterclockwise is not the goal

[@annalizamesina3512]

Hi kevin. I just want to share what i was thought in school, with regard to your "balloon" example.. From what i was thought, repeated letters should be placed with a null (X) in the middle. So balloon should be : ba lx lo on? just sharing... Thanks

[@videosbykevin2938]

You are quite right, Annaliza. Some people do as I have shown, others break apart all double letters as you were taught, and still others break only double letters that appear as a pair. Thank you for your comment.

[@Shadow017M]

@@videosbykevin2938 Potentially similar question, but what is to safeguard from palindrome words? Like noon, boob, etc. Say it was the word 'noon'. Could you put an x after the first n then do the double letter together then do the final N with the 5th letter and continue like that? I have my own workaround but I want to get the right system down first

[@d.s.1409]

Great explanation! But what happens if the letter j shows up in our plaintext.. do we subsitute it with an x maybe?

[@videosbykevin2938]

Thank you D. S. Personally, I use an i. No one would mistake ianuary, iury, or iaguar for anything but January, jury, or jaguar. But of course, you can use an X or any agreed upon letter. Another option would be to instead omit the letter Q, and use kw whenever it is needed as in kwick, kwit, or kwiet.

[@conanryoma7958]

Okkk, thanks. I think I am more clear about the playfair cipher now hahahah

[@jjpxggy9101]

Thank u soo much!!! xx

[@videosbykevin2938]

You are most welcome.

[@justmejhbmed9778]

Great video and well explained. Thanks a lot ! However, as you deliberately left out the “J”, I would like to know how I would send a “J” if I wanted to send a coded word like “ JUST “ or “ JUMP “ etc. I hope you will reply. Thanks again.

[@videosbykevin2938]

Greetings JustMe, Typically one would substitute I for J when needed. Few people would confuse IUST, IUMP, or IANuARY for anything but JUST, JUMP, or JANUARY. However, as long as you and your recipient agree beforehand, you can leave out any letter you wish. I chose J because that's what the original crafter of the cipher did and because it has an easy substitution in the letter I. Thank you for you kind praise, Kevin

[@justmejhbmed9778]

@@videosbykevin2938 thanks for your answer and taking time to reply. it's really a good way to keep private information for oneself, like passwords or bank details. thanks again.

[@MarcusVinicius-jc2em]

Obrigado por este vídeo.

[@ivanostermann7644]

Hello. Great video. Could you recommend a cipher book? thanks

[@videosbykevin2938]

Good day Ivan, There are many fine books on ciphers, but for the most in depth understanding, I would recommend you find a math textbook on Number Theory. It will be quite math-heavy and contain gads of information on many other topics, but the chapters on ciphers will be quite detailed with plenty of examples on both encoding and decoding. Thank you for watching, Kevin