Tags: misc stego
Rating:
#
Hallo?
### Challenge Text
>The flag is exactly as decoded. No curly brackets.
>NOTE: keep the pound symbols as pound symbols!
>~BobbaTea#6235, Klanec#3100
### Challenge Work
Listening to the audio we can tell that these are DTMF tones being entered. Maybe we can decipher them a-la T9?
First let us get the DTMF tones from the file. Make sure to compare outputs from both of these commands from `dtmf.py`. (https://github.com/ribt/dtmf-decoder)
```txt
dtmf-decoder [master●] % ffmpeg -i down.mp3 down.wav
dtmf-decoder [master●] % ./dtmf.py -v ../down.wav
0:00 ....................
0:01 ................777.
0:02 ..7.7...777.........
0:03 ....................
0:04 ....................
0:05 .........44.........
0:06 ....................
0:07 ..............222..2
0:08 2...................
0:09 ....................
0:10 ....22...2222..22...
0:11 ....................
0:12 ............888.....
0:13 ....................
0:14 ..........33...333..
0:15 .33.................
0:16 ....................
dtmf-decoder [master●] % ./dtmf.py -v -t 10 ../down.wav
[... for brevity]
```
Once we are satisfied with what we believe the DTMF to be we can decode it:
```python
#!/usr/bin/env python3
str_one = "777 4 22 222 8 333 # 999 33 33 8 # 3 8 3 333 # 8 666 66 33 7777 #"
t9_text = {
"2": "a",
"22": "b",
"222": "c",
"3": "d",
"33": "e",
"333": "f",
"4": "g",
"44": "h",
"444": "i",
"5": "j",
"55": "k",
"555": "l",
"6": "m",
"66": "n",
"666": "o",
"7": "p",
"77": "q",
"777": "r",
"7777": "s",
"8": "t",
"88": "u",
"888": "v",
"9": "w",
"99": "x",
"999": "y",
"9999": "z"
}
def getsinglenumbergroup(num_message):
char_str = num_message[0]
for char in num_message[1:]:
if char == char_str[-1]:
char_str += char
else:
break
return char_str
def getnumbergroups(num_message):
number_groups = []
while True:
try:
num_string = getsinglenumbergroup(num_message)
number_groups.append(num_string)
num_message = num_message[len(num_string):]
except:
break
return number_groups
def numberstowords(num_str_list, t9_text):
decoded_str = ""
for number in num_str_list:
try:
decoded_str += t9_text[number]
except:
decoded_str += number
return decoded_str
def getsentence(num_sentence):
decoded_sentence = ""
num_sentence = num_sentence.replace(".", "").replace(",", "").replace(":", "").replace("!","")
for word in num_sentence.split(" "):
word_groups = getnumbergroups(word)
decoded_sentence += numberstowords(word_groups, t9_text)
decoded_sentence += " "
return decoded_sentence.upper()
print(getsentence(str_one))
print()
# R P H C T F # Y E U # D T D F # T F E E S #
#RGBCTF#YEE#DTMF#TONES#
```
