Over the Wire - Krypton 2

Krypton 2


Objectives
The password for level 3 is in the file krypton3. It is in 5 letter group ciphertext. It is encrypted with a Caesar Cipher. Without any further information, this cipher text may be difficult to break. You do not have direct access to the key, however you do have access to a program that will encrypt anything you wish to give it using the key. If you think logically, this is completely easy.


Solution

ok so the first thing we did was link the file in a temp directory

krypton2@krypton:/krypton/krypton2$ mkdir /tmp/asmithkryp2
krypton2@krypton:/krypton/krypton2$ cd /tmp/asmithkryp2
krypton2@krypton:/tmp/asmithkryp2$ ln -s /krypton/krypton2/keyfile.dat 

Then we changed the permissions for everyone to have access to the file
krypton2@krypton:/tmp/asmithkryp2$ chmod 777 .

just like the example on the website
now we want to create a file that we will use to run the encrypt binary against
krypton2@krypton:/tmp/asmithkryp2$ echo "abcdefghijklmnopqrstuvwxyz" > alpha.txt
krypton2@krypton:/tmp/asmithkryp2$ cat  alpha.txt
abcdefghijklmnopqrstuvwxyz

now lets throw it at the encryption binary to see if we can figure out the shift

krypton2@krypton:/tmp/asmithkryp2$ /krypton/krypton2/encrypt ./alpha.txt
krypton2@krypton:/tmp/asmithkryp2$ cat ciphertext
MNOPQRSTUVWXYZABCDEFGHIJKL

so A becomes M so its a 12 shift of ROT12

so now we can try to decode the encrypted password in the krypton2 folder
we will use the translate cmd again but start at M instead of N
krypton2@krypton:/krypton/krypton2$ cat krypton3 | tr '[M-ZA-Lm-za-l]' '[A-Za-z]'
CAESARISEASY