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Fix the challenges, use the correct domain

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lucky-vers 2023-11-03 01:18:07 +05:30
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Phase 2/06 Other Domains.md
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# Domain: General Skills
# Domain: Cryptography
## Magikarp Ground Mission
## Mod 26
We press the `START INSTANCE` button and are given an ssh command to enter
**Flag:** `picoCTF{next_time_I'll_try_2_rounds_of_rot13_ulYvpVag}`
We are given the flag as `cvpbPGS{arkg_gvzr_V'yy_gel_2_ebhaqf_bs_ebg13_hyLicInt}`. This is a simple `ROT-13` cipher, a special case of the Caesar cipher in which the letters are shifted by 13 positions.
Putting this into any online `ROT-13` decoder (I used *https://rot13.com/*), we get `picoCTF{next_time_I'll_try_2_rounds_of_rot13_ulYvpVag}`.
## The Numbers
**Flag:** `PICOCTF{THENUMBERSMASON}`
We're given an image with a list of numbers along with opening and closing brackets.
![The Numbers](../Images/the_numbers.png)
It seems to be the flag with the letters encoded as their positions in the alphabet. We write some simple C code to decode it
```
ssh ctf-player@venus.picoctf.net -p 52353
#include <stdio.h>
int main()
{
int numbers[] = {
16, 9, 3, 15, 3, 20, 6, // The part before the brackets
20, 8, 5, 14, 21, 13, 2, 5, 18, 19, 13, 1, 19, 15, 14 // The part before the brackets
};
for (int i = 0; i < 22; i++) {
printf("%c", numbers[i] + 65);
}
return 0;
}
```
It's given that we need to login as `ctf-player` with the password `a13b7f9d`. Once we do, we're greeted to this
Compiling and running it, we get
```
ctf-player@venus.picoctf.net's password:
Welcome to Ubuntu 18.04.5 LTS (GNU/Linux 5.4.0-1041-aws x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
This system has been minimized by removing packages and content that are
not required on a system that users do not log into.
To restore this content, you can run the 'unminimize' command.
The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.
Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.
ctf-player@pico-chall$
~/Projects $ gcc main.c -o main
~/Projects $ ./main
QJDPDUGUIFOVNCFSTNBTPO
~/Projects $
```
Running `ls`, we get
```
ctf-player@pico-chall$ ls
1of3.flag.txt instructions-to-2of3.txt
```
Using `cat`, we get the first part of the flag and instructions to the next part
```
ctf-player@pico-chall$ cat *.txt
picoCTF{xxsh_
Next, go to the root of all things, more succinctly `/`
```
So we go to the root folder using `cd`
```
ctf-player@pico-chall$ cd /
ctf-player@pico-chall$ ls
2of3.flag.txt bin boot dev etc home instructions-to-3of3.txt lib lib64 media mnt opt proc root run sbin srv sys tmp usr var
```
We see two `.txt` files. Running `cat` on them, we get the second part of the flag
```
ctf-player@pico-chall$ cat *.txt
0ut_0f_\/\/4t3r_
Lastly, ctf-player, go home... more succinctly `~`
```
So we go to the home directory. Running `cd` with no arguments takes us there
```
ctf-player@pico-chall$ cd
ctf-player@pico-chall$ ls
3of3.flag.txt drop-in
```
Running `cat` for the third time, we get
```
ctf-player@pico-chall$ cat *.txt
71be5264}
```
As the third part of the flag.
Combining all the parts, we get the flag as `picoCTF{xxsh_` + `0ut_0f_\/\/4t3r_` + `71be5264}` = `picoCTF{xxsh_0ut_0f_\/\/4t3r_71be5264}`
**Flag:** `picoCTF{xxsh_0ut_0f_\/\/4t3r_71be5264}`
## 2Warm
The problem statement here is simple— to convert the number 42 from base 10 to binary. We use the `bc` (basic calculator) command for this
```
~ $ echo "obase=2; 42" | bc
101010
```
Here, we're setting the `obase` variable to 2, indicating we want to convert the decimal integer to its binary form. As a result, we get `101010`. Thus, our flag becomes `picoCTF{101010}`.
**Flag:** `picoCTF{xxsh_0ut_0f_\/\/4t3r_71be5264}`
This seems to be a Caesar cipher. Using the solver on [dcode](https://www.dcode.fr/caesar-cipher) and decrypting it using brute-force, we get the answer as `PICOCTFTHENUMBERSMASON`.