CTF NO : 6

Hello there, welcome to another write-up. Today, we are going to slove an easy Reverse Engineering problem.

Challenge Details:

Topic: Reverse Engineering

Flag Format: IHC_CTF{}

CTF Link: https://t.me/ctf_invisiblehc/11

Description:

Python is awesome for beginner. A lot of work can be done easily with it. Download this python file to find the flag.

Solution:

The problem code:

flag = "IHC_CTF{_________}"

c = 0

result = ""

while c < len(flag):

    a = chr(ord(flag[c])-15)

    result = result + a

    c = c + 1

print(result)

#Result is ":94P4E7lC$G$C&6P"DP"?($C$D("?8n"

The provided code attempts to decrypt the flag by shifting each character 15 positions backward in the ASCII table.

To solve this challenge, we first reversed the decryption process by shifting the ASCII values of the cipher text characters by +15 instead of -15.

The flag format is IHC_CTF{...} but it has been removed, and the cipher text has been assigned to the "flag" variable.

Also, the double quotation marks in the cipher text should be replaced with single quotation marks in the Python code to avoid syntax errors. Once you make this change, run the decryption code, and you will get the flag.

Solution code:

flag = ':94P4E7lC$G$C&6P"DP"?($C$D("?8n'

c = 0

result = ""

while c < len(flag):

    a = chr(ord(flag[c])+15)

    result = result + a

    c = c + 1

print(result)

After running The Solution Code,

We Finally Found The Flag: IHC_CTF{R3V3R5E_1S_1N73R3S71NG}

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