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Cryptanalysis of ciphertext using Java

I am looking for some assignment ideas.

I have 7 encrypted text files, all of which are encrypted using the same symmetric key, which is 3 characters long and is alphabetic . An encryption algorithm is not provided, but specifications indicate that it is a home-made algorithm and naive (whatever that means). My goal is to decrypt these files. I'm just looking for ideas about attacks that I can execute in these files.

So far I have done frequency analysis, a brute force attack to detect Ceasar Cipher, Krasinsky's method to detect Vigenere Cipher, Ciphertext XOR to detect a simple version of stream encryption. I suspect the files were encrypted using some combination of ciphers.

By the way, the decrypted plaintext should contain only a simple message, but the encrypted text shows the use of more than 97 different ASCII characters!

Any general help, ideas or directions are welcome! Honestly, I should not decrypt these files, but then I could also prove that my professor is wrong with your help. Thank!

EDIT

I am looking for attacks on block or stream ciphers. At least this is what I suspect ...

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Enigma 3 . 97 ASCII? ASCII 32 126, 94 . \N \r 96, , , \0 97. , Engima ( ), Windows .

. , , . , , . , .

, . , , .

, Enigma, , . , 10 ^ 15 .

+3

, :

  • XOR
  • XOR 1-
  • XOR /: /

, , , , ASCII /.

+1

Now you said you did a statistical analysis. If the algorithm is actually naive, the symbol frequencies will not be evenly distributed. Some characters will be found more often. This is true? If so, I would be from there from there.

I could also prove that my professor is wrong with your help

With "our help" we will prove that your professor is wrong.

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