kashiCTF 2026 - Ancient Mystery

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A secret message has been passed down through generations since the time of the great Mahabharata war. Legend says that every 64 years, the keepers of this secret would encode the message once more to protect it from those who might seek to misuse its power. The message has traveled through 3136 years of history, from the ancient battlefields of Kurukshetra in 3136 BCE to the dawn of the Common Era.

Initial Analysis

The challenge provides two main clues:

  1. Mathematical Clue: The message has existed for 3136 years and was re-encoded every 64 years. $$\frac{3136}{64} = 49$$ This suggests the message has been recursively encoded 49 times.
  2. File Inspection: The provided file secret_message.txt is large (~59MB) and starts with the characters Vm0wd2Qy..., which is a classic signature for multiple layers of Base64 encoding.

Extraction & Decoding

We can use a Python script to iteratively decode the file 49 times. Each layer of decoding reduces the file size until the final plaintext flag is revealed.

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import base64

def solve():
    # Read the initial encoded data
    with open('secret_message.txt', 'r') as f:
        data = f.read().strip()

    # Iteratively decode 49 times
    print("[*] Starting iterative Base64 decoding...")
    for i in range(49):
        try:
            data = base64.b64decode(data).decode('utf-8')
        except Exception as e:
            print(f"[-] Error at iteration {i+1}: {e}")
            break

    print(f"[+] Final Decoded Message: {data}")

if __name__ == "__main__":
    solve()

Flag

kashiCTF{th3_s3cr3t_0f_mah4bh4r4t4_fr0m_3136_BCE}