Krypton Level 3 to Level 5 | Basic Cryptographic Techniques
Learn basic cryptographic techniques by playing Krypton wargame from OverTheWire. Below is the solution of Level 3 → Level 4, Level 4 → Level 5 and Level 5 → Level 6.
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Krypton Level 3 → Level 4
Level Info
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!)
Solution
Command to login ssh krypton3@krypton.labs.overthewire.org -p 2222 and password is CAESARISEASY .
First lets change to directory where we will find krypton4 . cd /krypton/krypton3
In the directory there are found1, found2 and found3 files which are encrypted using same key. These files contains the encrypted text like krypton4.
Using these files and an automated cryptogram solver quipquip, we can crack the password.
First copy all the content of files found1, found2 and found3 in the puzzle box and click solve. The output we get make sense, so it has decrypted the text.
Now in another tab enter the content of file krypton4, but there are nine possible output.
Since the quipquip produced only one output when we ran it with the content of found1, found2 and found3. So we can add the content of krypton4 with the content of these files. We have added the content of krypton4 file at the end, so our password will be at the end. The decrypted text at the end is DONE THE LEVEL FOUR PASSWORD IS BRUTE. So password for next level is BRUTE .
Krypton Level 4 → Level 5
Level Info
An example of a polyalphabetic cipher is called a Vigenère Cipher. It works like this:
If we use the key(K) ‘GOLD’, and P = PROCEED MEETING AS AGREED, then “add” P to K, we get C. When adding, if we exceed 25, then we roll to 0 (modulo 26).
P P R O C E E D M E E T I N G A S A G R E E D\
K G O L D G O L D G O L D G O L D G O L D G O\
becomes:
P 15 17 14 2 4 4 3 12 4 4 19 8 13 6 0 18 0 6 17 4 4 3\
K 6 14 11 3 6 14 11 3 6 14 11 3 6 14 11 3 6 14 11 3 6 14\
C 21 5 25 5 10 18 14 15 10 18 4 11 19 20 11 21 6 20 2 8 10 17\
So, we get a ciphertext of:
VFZFK SOPKS ELTUL VGUCH KR
This level is a Vigenère Cipher. You have intercepted two longer, english language messages. You also have a key piece of information. You know the key length!
For this exercise, the key length is 6. The password to level five is in the usual place, encrypted with the 6 letter key.
Solution
Command to login ssh krypton4@krypton.labs.overthewire.org -p 2222 and password is BRUTE .
Read The Vigenère Cipher Encryption and Decryption
In directory /krypton/krypton4 , file kryton5 contains the encrypted password of the next level. We know the key length is 6. We will use Vigenère Cipher – Decoder to get the key and then the password.
In content in file found1 and found2 will help to find us the key. Copy the content of found1 and found2 in the decoder on the website and enter key length 6.
The first decrypted text make sense and the key we get from here is FREKEY.
Now enter the encrypted password from the file krypton5 in the decoder box and the key FREKEY in the key section. The output we get is CLEAR TEXT, and the password for the next level is CLEARTEXT.
Krypton Level 5 → Level 6
Level Info
FA can break a known key length as well. Lets try one last polyalphabetic cipher, but this time the key length is unknown.
Enjoy.
Solution
Command to login ssh krypton5@krypton.labs.overthewire.org -p 2222 and password is CLEARTEXT .
Change into directory /krypton/krypton5. We have found1, found2 and found3 files which will help us. We do not know key length and key.
We can use Vigenère Cipher – Decoder to get the key. Copy the content of files found1, found2 and found3 in the decoder box and click Automatic Decryption. The first output make sense and the key is KEYLENGTH.
Now copy the encrypted text from file krypton6 and enter the key. The ouput we get is RANDO M and the password is RANDOM .
