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.

Login

ssh bandit11bandit.labs.overthewire.org -p 2220
dtR173fZKb0RRsDFSGsg2RWnpNVj3qRr

Sources

Ascii code

Doc

cat (1)              - concatenate files and print on the standard output

Solution

By using cat we get the contents of the single file present in the directory. We can see that the present data makes up a string. By simply rotating every character in this string ascendingly by the value 13 we could in theory get the correct answer. I`ve copied the output from data.txt into my own terminal, made a c++ program that increases each element in a character array by 13 and then print out the answer.

bandit11@bandit:~$ ls
data.txt
bandit11@bandit:~$ cat data.txt
Gur cnffjbeq vf 7k16JArUVv5LxVuJfsSVdbbtaHGlw9D4

C++ code and compilation

#include <iostream>
using namespace std;

//Gur cnffjbeq vf 7k16JArUVv5LxVuJfsSVdbbtaHGlw9D4
//rot by 13

char v[100] = {'G', 'u', 'r', ' ', 'c', 'n', 'f', 'f', 'j', 'b', 'e', 'q', ' ', 'v', 'f', ' ', '7', 'k', '1', '6', 'J', 'A', 'r', 'U', 'V', 'v', '5', 'L', 'x', 'V', 'u', 'J', 'f', 's', 'S', 'V', 'd', 'b', 'b', 't', 'a', 'H', 'G', 'l', 'w', '9', 'D', '4'};

int main() {
    for (int i = 0; i < 48; i++) {
        if (v[i] >= 'A' && v[i] <= 'Z') {
            v[i] = (v[i] - 'A' + 13) % 26 + 'A';
        }
        else if (v[i] >= 'a' && v[i] <= 'z') {
            v[i] = (v[i] - 'a' + 13) % 26 + 'a';
        }
    }
    for (int i = 0; i < 48; i++) {
        cout << v[i];
    }
    return 0;
}

02:09:33 archie@Archie c++ → g++ decrypt.cpp  -o out
02:10:29 archie@Archie c++ → ./out
The password is 7x16WNeHIi5YkIhWsfFIqoognUTyj9Q4