Rating:
# CR1 - Ultracoded
## Challenge
> Fady didn't understand well the difference between encryption and encoding, so instead of encrypting some secret message to pass to his friend, he encoded it!
> Hint: Fady's encoding doens't handly any special character
> [zero_one](zero_one)
## Solution
`zero_one` is a text file containing only the words `ZERO` and `ONE` in some kind of repeating pattern. I figured this must be converted into a binary representation, so I wrote a small python script.
```
#!/usr/bin/python2.7
import binascii
import base64
data = open("zero_one").read()
dataArr = data.split()
binaryBuffer = ""
for w in dataArr:
if "ZERO" in w:
binaryBuffer += "0"
if "ONE" in w:
binaryBuffer += "1"
```
I converted the buffer string to an integer and used `binascii.unhexlify` to return the ASCII plaintext.
```
n = int(binaryBuffer, 2)
binDecoded = binascii.unhexlify('%x' % n)
```
Printing `binDecoded` reveals a base64-encoded string.
```
Li0gLi0uLiAuIC0uLi0gLS4tLiAtIC4uLS4gLSAuLi4uIC4tLS0tIC4uLi4uIC0tLSAuLS0tLSAuLi4gLS0tIC4uLi4uIC4uLSAuLS0uIC4uLi0tIC4tLiAtLS0gLi4uLi4gLiAtLi0uIC4tLiAuLi4tLSAtIC0tLSAtIC0uLi0gLQ==
```
Let's decode it!
```
base64Decoded = base64.b64decode(binDecoded)
```
Printing this output produces something resembling morse code.
```
.- .-.. . -..- -.-. - ..-. - .... .---- ..... --- .---- ... --- ..... ..- .--. ...-- .-. --- ..... . -.-. .-. ...-- - --- - -..- -
```
I couldn't find a library to decode morse code, so I built the decoded string from a python dictionary.
```
CODE = {'.-': 'A', '-...': 'B', '-.-.': 'C',
'-..': 'D', '.': 'E', '..-.': 'F',
'--.': 'G', '....': 'H', '..': 'I',
'.---': 'J', '-.-': 'K', '.-..': 'L',
'--': 'M', '-.': 'N', '---': 'O',
'.--.': 'P', '--.-': 'Q', '.-.': 'R',
'...': 'S', '-': 'T', '..-': 'U',
'...-': 'V', '.--': 'W', '-..-': 'X',
'-.--': 'Y', '--..': 'Z',
'-----': '0', '.----': '1', '..---': '2',
'...--': '3', '....-': '4', '.....': '5',
'-....': '6', '--...': '7', '---..': '8',
'----.': '9'
}
morseDecoded = ''.join(CODE.get(i) for i in base64Decoded.split())
```
Printing this output gave me something closely resembling the flag format.
```
ALEXCTFTH15O1SO5UP3RO5ECR3TOTXT
```
The hint in the challenge description mentioned that special characters weren't handled. After some experimentation, I determined that the O's were underscores and that the curly brackets were simply missing. Here's the final part of the python script.
```
morseList = list(morseDecoded.lower())
alexCTF = ''.join(morseList[0:7])
flag = ""
for l in morseList[7:]:
if "o" in l:
flag += "_"
else:
flag += l
print "The flag is: " + alexCTF + "{" + flag + "}"
```
This yields the flag.
```
The flag is: alexctf{th15_1s_5up3r_5ecr3t_txt}
```
