Bandit: Level 11 - Level 12

Level 11

Username: bandit11
Password: dtR173fZKb0RRsDFSGsg2RWnpNVj3qRr

Task:

https://overthewire.org/wargames/bandit/bandit12.html

The password for the next level is stored in the file data.txt, where all lowercase (a-z) and uppercase (A-Z) letters have been rotated by 13 positions

Commands you may need to solve this level
grep, sort, uniq, strings, base64, tr, tar, gzip, bzip2, xxd

Helpful Reading Material
Rot13 on Wikipedia

Start

Let’s begin by connecting to the server bandit.labs.overthewire.org and logging in with user bandit11 on port 2220.

We have several commands available for this task:

man (1)              - an interface to the system reference manuals
grep (1)             - print lines that match patterns
sort (1)             - sort lines of text files
uniq (1)             - report or omit repeated lines
strings (1)          - print the sequences of printable characters in files
base64 (1)           - base64 encode/decode data and print to standard output
tr (1)               - translate or delete characters
tar (1)              - an archiving utility
gzip (1)             - compress or expand files
bzip2 (1)            - a block-sorting file compressor, v1.0.8
xxd (1)              - make a hex dump or do the reverse.

Solve the level

Okay I think we have to do a little research on Rot13.

This helpful table is a good visual what we have to do here. We have to translate the letters 13 positions back. The trcommand looks like the correct choice here. Lets check the manual.

The manual is a little bit difficult to understand here:

NAME
       tr - translate or delete characters

SYNOPSIS
       tr [OPTION]... STRING1 [STRING2]

DESCRIPTION
       Translate,  squeeze, and/or delete characters from standard input, writing to standard output.  STRING1 and STRING2 specify arrays of characters ARRAY1 and
       ARRAY2 that control the action.

What is meant with that?

• OPTION Optional flags
• STRING1 is the set of characters what we want to translate/delete.
• STRING2 is the set of characters we want to translate into

For ROT13 encoding or decoding, you use tr to map each letter of the alphabet to its counterpart 13 positions ahead.

We use STRING1 for our characters, what we want:

"A-Za-z" is our alphabet with upper and lower letters

We use STRING2 for our characters, what we want replaced with: "N-ZA-Mn-za-m" is the ROT13 alphabet, check the picture above. The upper alphabet goes “N-Z + A-M” and the lower alphabet goes “n-z + a-m”.

Lets take all this in one command:

bandit11@bandit:~$ cat data.txt | tr 'A-Za-z' 'N-ZA-Mn-za-m'
The password is 7x16WNeHIi5YkIhWsfFIqoognUTyj9Q4

We send the ouput of the data.txt file into the “translator” with our prefered translation and get the password as output :joy:

Password: 7x16WNeHIi5YkIhWsfFIqoognUTyj9Q4

Explanation:

Substitution Ciphers

Substitution involves replacing one character with another. Substitution ciphers, such as the Caesar and Vigenère ciphers, have been used for a long time but are no longer considered secure.

The ROT13 cipher, a simple substitution cipher, rotates letters by 13 positions in the alphabet. This is particularly interesting because, with a 26-letter Latin alphabet, the encryption algorithm is the same as the decryption algorithm.

In Linux, the tr command, which stands for ‘translate’, is used for character replacement. The basic syntax for tr is:

tr <old_chars> <new_chars>