Krypton3 - krypton4
Well done. You've moved past an easy substitution cipher.
Hopefully you just encrypted the alphabet a plaintext to fully expose the key in one swoop.
The main weakness of a simple substitution cipher is repeated use of a simple key. In the previous exercise you were able to introduce arbitrary plaintext to expose the key. In this example, the cipher mechanism is not available to you, the attacker.
However, you have been lucky. You have intercepted more than one message. The password to the next level is found in the file 'krypton4'. You have also found 3 other files. (found1, found2, found3)
You know the following important details:
- The message plaintexts are in English (*** very important)
- They were produced from the same key (*** even better!)
Used http://quipqiup.com/index.php to solve the found1 file.
Once this was done, it was possible to line up the clear-text and encrypted text to figure out the key.
Once that was found the 'tr' command in linux can do the translation.
krypton3@melinda:/games/krypton/krypton3$ cat krypton4 | tr QAZWSXEDCRFVTGBYHNUJMIKOLP ABCDEFGHIJKLMNOPQRSTUVWXYZ WELLD ONETH ELEVE LFOUR PASSW ORDIS BRUTE
Which can be read as: WELL DONE THE LEVEL FOUR PASSWORD IS BRUTE