# Description Starfleet has received a transmission from Bynaus. However, the message apears to be blank. Is there some kind of hidden message here?
MD5(transmission.txt) = 736b9d6c408c3c75559c45083413c10a
![image](https://user-images.githubusercontent.com/101048320/234386677-38ddc7f2-1163-48e9-8f05-c8d7e578391a.png)
# Files 
- transmission.txt 
## Solution# Recon
- I started with a simple file analysis command `file transmission.txt` : ```┌─[not1cyyy@0x45] - [~/Desktop/space-heroes-CTF/2023/Bynary_Encoding_FINISHED] - [mar. avril 25, 20:48]└─[$] <> file transmission.txt transmission.txt: ASCII text```
- Okay, let's run `cat transmission.txt` and see what this file contai... oh : ```┌─[not1cyyy@0x45] - [~/Desktop/space-heroes-CTF/2023/Bynary_Encoding_FINISHED] - [mar. avril 25, 20:50]└─[$] <> cat transmission.txt                                                    
```
## Trial and Error 
- I figured out this is some type of whitespace encoding, so I used the tool `stegsnow` and got nothing, literally : ```┌─[not1cyyy@0x45] - [~/Desktop/space-heroes-CTF/2023/Bynary_Encoding_FINISHED] - [mar. avril 25, 20:52]└─[$] <> stegsnow transmission.txt ┌─[not1cyyy@0x45] - [~/Desktop/space-heroes-CTF/2023/Bynary_Encoding_FINISHED] - [mar. avril 25, 20:52]└─[$] <> ```- After hexdumping the file with `xxd`, I saw something interesting : ```┌─[not1cyyy@0x45] - [~/Desktop/space-heroes-CTF/2023/Bynary_Encoding_FINISHED] - [mar. avril 25, 20:52]└─[$] <> xxd transmission.txt 00000000: 2009 0909 2020 0909 0a20 0909 2009 2020   ...  ... .. .  00000010: 200a 2009 0920 2020 0909 0a20 0909 0920   . ..   ... ... 00000020: 0920 200a 2009 0920 2009 0920 0a20 0909  .  . ..  .. . ..00000030: 0909 2009 090a 2009 0920 2020 2009 0a20  .. ... ..    .. 00000040: 0920 0909 0909 090a 2009 0920 2020 0920  . ...... ..   . 00000050: 0a20 0909 2009 0920 200a 2020 0909 2020  . .. ..  .  ..  00000060: 2009 0a20 0909 2009 0909 200a 2009 0920   .. .. ... . .. 00000070: 2009 2020 0a20 0920 0909 0909 090a 2009   .  . . ...... .00000080: 0920 0909 2009 0a20 2009 0920 0920 200a  . .. ..  .. .  .00000090: 2009 0920 0909 0920 0a20 0920 0909 0909   .. ... . . ....000000a0: 090a 2009 0909 2009 2020 0a20 2009 0920  .. ... .  .  .. 000000b0: 2009 090a 2009 0920 2020 2009 0a20 0909   ... ..    .. ..000000c0: 2020 2009 090a 2009 0920 0920 2020 0a20     ... .. .   . 000000d0: 0909 2009 2020 090a 2009 0920 0909 0920  .. .  .. .. ... 000000e0: 0a20 0909 2020 0909 090a 2009 2009 0909  . ..  .... . ...000000f0: 0909 0a20 0909 2020 2020 090a 2009 0920  ... ..    .. .. 00000100: 0909 0920 0a20 0920 0909 0909 090a 2020  ... . . ......  00000110: 0909 2009 2020 0a20 0909 2009 0909 200a  .. .  . .. ... .00000120: 2009 0920 2009 2020 0a20 0909 0920 2009   ..  .  . ...  .00000130: 200a 2020 0909 2020 2020 0a20 0909 2009   .  ..    . .. .00000140: 2020 090a 2009 0920 2009 2020 0a20 0920    .. ..  .  . . 00000150: 0909 0909 090a 2009 0920 0920 2020 0a20  ...... .. .   . 00000160: 2009 0920 2020 200a 2009 0909 2009 0909   ..    . ... ...00000170: 0a20 0920 0909 0909 090a 2009 0909 2009  . . ...... ... .00000180: 2020 0a20 0909 2009 0909 090a 2009 2009    . .. ..... . .00000190: 0909 0909 0a20 0909 0920 2020 200a 2009  ..... ...    . .000001a0: 0920 2020 2009 0a20 2009 0920 2020 090a  .    ..  ..   ..000001b0: 2009 0920 0909 0920 0a20 0909 0920 0920   .. ... . ... . 000001c0: 200a 2009 0909 0909 2009 0a               . ..... ..```
- It's not just whitespaces ! there are some values in there ! 
# Execution
- I went ahead and opened the file with python : ```pythonf = open('transmission.txt', 'rb')
for i in f.read():
    print(i)```
- Here's some of what the script outputs : ```─[not1cyyy@0x45] - [~/Desktop/space-heroes-CTF/2023/Bynary_Encoding_FINISHED] - [mar. avril 25, 20:57]└─[$] <> python3 solve.py | head 329993232991032```
- Interesting, so we know we have mainly 32 and 9 as our values, as the challenge hints, this is binary encoding, where one byte represents the value of 1 and the other represents the value of 0. I wrote this python script to solve the challenge : 
```pythonf = open('transmission.txt', 'rb')
binary = ''
def decode_binary_string(s):    return ''.join(chr(int(s[i*8:i*8+8],2)) for i in range(len(s)//8))
for i in f.read():
    if i == 32:
        binary += '0'    elif i == 9:
        binary += '1'
print(decode_binary_string(binary))```- After running the script, we get the flag : ```┌─[not1cyyy@0x45] - [~/Desktop/space-heroes-CTF/2023/Bynary_Encoding_FINISHED] - [mar. avril 25, 20:59]└─[$] <> python3 solve.py shctf{a_bl1nd_m4n_t3aching_an_4ndr0id_h0w_to_pa1nt}```
# Flag shctf{a_bl1nd_m4n_t3aching_an_4ndr0id_h0w_to_pa1nt}
