Cryptography - Breaking the Vigenere Cipher
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- čas přidán 30. 06. 2024
- In this video I go over how to use my Vigenere frequency tool to figure out the keyword used to encrypt a message using the Vigenere Cipher.
All my encryption links are at www.brianveitch.com/maze-runner/
Thank you The program is very well done, visual and easy to follow. Impressive!
Wow your program is very cool man!
Your tool is awesome!
This is great! Thanks!!!
this was very helpful thank you
Could you post a link to the Vigenere frequency tool you used in this video?
I uploaded the page here: www.brianveitch.com/maze-runner/frequency-analysis-vigenere/
Wasn't this similar to how the Enigma was broken? Or was it this method itself?
An extremely complex version of the Vigenere cipher if that helps. The idea is similar in that each letter typed uses substitutions to get to an ouput. After a letter has been typed a new substitution is used. The A quick search online I came across www.counton.org/explorer/codebreaking/enigma-cipher.php which might help.
There are videos about it on SciShow, Khanacademy, etc. that might give a good demonstration.
hello, i found keyword length 3 is more than length 9. Why do you choose length 9 not 3
Honestly, I should have. But 9 showed up quite a bit and I already knew the keylength was 9. Also because 3 is a factor of 9, 3 will show up more. I would assume someone trying this type of cipher would probably choose a word longer than 3. If you use such a small word, the frequency distribution of every 3rd letter would be extremely close looking to the frequency of the English language. Longer words mean you won't have much of a frequency distribution to look at. So seeing 9 show up that often was a good indicator that 9 was it.
Could you post a link to the Vigenere Decryptor ( the very last step of this video )
All my encryption/decryption links are at www.brianveitch.com/mathcamp/cryptography/
At 3:28
you say that you are good with 'C', but how exactly are you getting the letter c? I don't get the whole frequency matching step at all, sorry.
FatherlyNick You can watch my video on Frequency analysis here if you have no background in how frequency analysis works: czcams.com/video/mUoQhXWTKE0/video.html
To understand this video, you will need to understand how the Vigenere cipher works. If you don't know that part yet do a search on CZcams. But watch a few videos because some of them are really confusing. In fact, most of them will probably be confusing. It was hard for me to wrap my head around the first time.
Warning: I'm going to try to explain how the Vigenere deciphering works in writing. This will almost certainly not make sense. I read it over before posting and I'm iffy about how well I explained it. Before reading, please watch a Vigenere cipher video. It will help with my explanation.
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We assume the codeword is 9 letters. The first thing we do is tally up every 9 letters starting with the 1st letter. This means we count the 1st, 10th, 19th, 28th, etc. until we've gone through the entire ciphertext. Then we make a frequency table (or frequency bar graph) of these letters.
When you have a ciphertext large enough then the frequency of letters should match closely to the frequency of letters used in the alphabet. For example, E is the most used letter in the English language. Since G is the most frequently used letter in the ciphertext, then we can shift all the letters so E and G match.
Since the codeword is 9 letters long, this means every 9 letters in the ciphertext will use the above frequency transformation. For example, the first letter in the ciphertext is F. Using this specific transformation that means F decrypts back to D. The 10th letter in the ciphertext is E. The transformation says that E should decrypt back to C. This transformation will only work for the 1st, 10th, 19th, 28th, etc. The other letters use a different transformation.
To figure out the 2nd letter in the codeword, count the frequency of every 9 letters starting with the 2nd letter (2nd, 11th, 20th, 29th, etc.). Then we shift so the frequency so E matches with the most frequent letter. It doesn't always match up perfectly. Statistically E is the most frequent but it might not be when your ciphertext is only a couple of paragraphs. That's why we use the bar graph. It lets us look at the frequency of all the letters (not just the most frequent).
Sorry again for this explanation.
Hello, thanks for the effort done.
The link is not working anymore, can you provide a valid one.
Regards.
+Mustafa Kaiiali Thanks for the message. I cleaned out my website and forgot to add these links back in. I changed the link in the description to a page where you can find the tool.
+Brian Veitch Thanks again
Where can i find this tool from?
Try one of these pages: www.brianveitch.com/mathcamp/cryptography/frequency-analysis-vigenere/index.html or www.brianveitch.com/maze-runner/frequency-analysis-vigenere/. I'm not sure if one is more updated than the other.
thk :)