Level 11 → 12

Level Goal

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

Write-Up

1. List the content of the current directory:

ls

This confirms the presence of the data.txt file.

1. Display the content of the data.txt file:

cat data.txt

This revealed a string of text with rotated letters.

1. To decode the ROT13 cipher, the tr (translate) command was used:

cat data.txt | tr 'A-Za-z' 'N-ZA-Mn-za-m'

• cat data.txt: Outputs the content of the file

• |: Pipes the output to the next command

• tr 'A-Za-z' 'N-ZA-Mn-za-m': Translates the rotated letters back to their original positions

The retrieved password: 7x16WNeHIi5YkIhWsfFIqoognUTyj9Q4

1. Access the next level:

ssh [e-mail] -p 2220

Enter the password when prompted.

Lessons Learned

• ROT13 is a simple letter substitution cipher that rotates letters by 13 positions

• The tr command in Unix is versatile for character-level text transformations

• Simple ciphers like ROT13 can be decoded using basic command-line tools

-- Othmane