Maznah Legacy

Challenge Overview

• Event: Bahtera 3108 2025
• Category: Reverse Engineering
• Points: 100
• Provided materials: kunci_diraja and output.txt

Iron Lady? Adakah itu Iron Man versi wanita? 🤔 Ataupun sebenarnya tokoh lain yang cukup terkenal di Malaysia?

Hanya dengan bedah program ini, anda akan tahu kebenarannya disebalik sosok misteri tersebut…

The challenge directory contained the binary, an IDA database, the text output, and the solver created during analysis.

The values in output.txt were:

[93, 92, 92, 101, 42, 0, 100, 29, 18, 9, 35, 29, 34, 45, 24, 10, 45, 107, 35, 112, 50, 111, 51, 33, 7, 45, 55, 121, 49, 123, 40, 15, 54, 123, 59, 125, 60, 57, 78]

Analyzing the Binary

I opened kunci_diraja in IDA and inspected the decompiled main function. The program processes each character of the supplied argument together with its index and compares the calculated result with the corresponding value in a 39-byte target array.

Because the validation operation is deterministic, I reversed it by trying every printable ASCII character for each target value. The following decoder reproduces the calculation from the decompiled program and keeps the character whose result matches:

key = [
    93, 92, 92, 101, 42, 0, 100, 29, 18, 9,
    35, 29, 34, 45, 24, 10, 45, 107, 35, 112,
    50, 111, 51, 33, 7, 45, 55, 121, 49, 123,
    40, 15, 54, 123, 59, 125, 60, 57, 78,
]


def reverse_char(v9, i):
    # Brute-force all printable ASCII
    for c in range(32, 127):
        v8 = (33818641 * (c + i + 42)) >> 32
        v9_calc = c + i + 42 - 127 * (
            (v8 + ((c + i + 42 - v8) >> 1)) >> 6
        )
        if v9_calc == v9:
            return chr(c)
    return "?"  # fallback if no match


result = "".join(reverse_char(k, i) for i, k in enumerate(key))
print("Recovered input:", result)

I saved the script as decoder.py and ran it with Python 3:

python3 decoder.py

The decoder returned:

Recovered input: 3108{P4k_Ungku_Pr0f3s0r_Dir4j4_Ek0n0mi}

Flag

3108{P4k_Ungku_Pr0f3s0r_Dir4j4_Ek0n0mi}