Challenge Description
- Challenge Name: Scrambled Egg
Hmm, I found this executable that should allow us access to some juicy innovation projects. But it asks for a key. Hmm, I’m stumped. Get the Key for me, please!
Explanation
I started out by open the given file in IDA to decompile it and view the code.
After understanding the graph view, it seems to be checking for different character each time.
The character seems to be very random to me. After trying to understand the graph view, I tried to understand the exe file by reading the pseudocode view.
It is easier to understand in pseudocode view. Based on what I understand, the code has a do while loop where it check if v7 has 31 character. After checking it is 31 character, it started to check the array number of v7 with different decimal number in a random order. I tried to convert the decimal number into character and save it into the list to print it out using python.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
v7 = list(range(1, 32))
v7[17] = chr(68)
v7[23] = chr(114)
v7[18] = chr(95)
v7[20] = chr(95)
v7[21] = chr(53)
v7[14] = chr(56)
v7[12] = chr(65)
v7[8] = chr(110)
v7[27] = chr(76)
v7[22] = chr(67)
v7[2] = chr(115)
v7[10] = chr(99)
v7[6] = chr(123)
v7[29] = chr(100)
v7[4] = chr(116)
v7[26] = chr(56)
v7[3] = chr(99)
v7[11] = chr(114)
v7[28] = chr(51)
v7[19] = chr(100)
v7[30] = chr(125)
v7[15] = chr(76)
v7[24] = chr(97)
v7[5] = chr(102)
v7[13] = chr(77)
v7[1] = chr(105)
v7[0] = chr(117)
v7[25] = chr(77)
v7[7] = chr(117)
v7[9] = chr(53)
v7[16] = chr(51)
print("".join(v7))
The result of v7 is a flag which is also the key
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
python solution.py
uisctf{un5crAM8L3D_d_5CraM8L3d}
Hold Up!. Enter the key to access secret Innovation Projects: uisctf{un5crAM8L3D_d_5CraM8L3d}
Answer Received!. Checking...
Key Verified. Here are unscrambled eggs for your troubles.
.-~-.
.' '.
/ \
.-~-. : ;
.' '.| |
/ \ :
: ; .-~""~-,/
| /` `'.
: | \
\ | /
`. .' \ .'
`~~~` '-.____.-'
Art Credit: jgs
Source: https://ascii.co.uk/art/egg
Things I learned from the challenge
- Sometimes try use pseudocode view in IDA as it helps alot
- Trying to write script is fun but time consuming
- Debug is not needed here ~
- I’m not good at reverse