In this level the password is stored in the file data.txt where all lowercase and uppercase letters have been rotated by 13 positions.
To decode the ceaser cipher we need to use the command tr. This is a command that can translate characters in strings.
tr <original_pattern> <new_pattern>
We need to shift both uppercase and lowercase characters. Our original characters are A-Za-z, because we have both uppercase and lowercase letters. Shift by 13 gives us the pattern N-ZA-Mn-za-m. So A maps to N, B to O etc.
cat data.txt | tr 'A-Za-z' 'N-ZA-Mn-za-m'
This command reveals the password: JVNBBFSmZwKKOP0XbFXOoW8chDz5yVRv