fibon.py

# Loading fibonacci
fib_nums = []
with open("fib.txt", "r+") as fib:
    lines = fib.readlines()
    for line in lines:
        fib_nums.append(int(line.strip()))


# Loading bytes
kipod_bytes = []
with open("out.split.txt", "r+") as kipod_file:
    kipod_lines = kipod_file.readlines()
    for kipod_line in kipod_lines:
        kipod_bytes.append(kipod_line.strip())

# Some key (marking) chars
k_boi = "01001011"
a_boi = "01000001"
f_boi = "01000110"
curly_boi = "01111011"
closing_boi = "01111101"


# Convert bit string to an ascii char
def bits2ascii(bits):
    bits = int(bits, 2)
    try:
        return bits.to_bytes((bits.bit_length() + 7) // 8, 'big').decode()
    except UnicodeDecodeError:
        return ""


# Create a string from chars at indexes from fibonacci sequence
# starting at base_offset
def make_fibon_string(base_offset):
    fibon = ""

    for fib_offset in fib_nums:
        total_offset = base_offset + fib_offset
        char = kipod_bytes[total_offset]

        fibon += char
        if char == closing_boi:
            break

    flag = bits2ascii(fibon)
    if flag.startswith("KAF{") and flag.endswith("}"):
        return flag

    return ""


for byte_idx in range(len(kipod_bytes)):
    byte = kipod_bytes[byte_idx]
    if byte == k_boi:

        # scan next following fib bytes from current position
        for fib_idx in range(len(fib_nums)):
            try:
                next_byte_p0 = kipod_bytes[byte_idx +
                                           fib_nums[fib_idx]]      # fib(n)

                next_byte_p1 = kipod_bytes[byte_idx +
                                           fib_nums[fib_idx + 1]]  # fib(n+1)

                # Check if the next bytes are 'A' and 'F' (flag beginning)
                if next_byte_p0 == a_boi and next_byte_p1 == f_boi:
                    # -1 because byte_idx points at 'K'
                    # and we have to start from before that
                    fibon_str = make_fibon_string(byte_idx - 1)
                    if fibon_str != "":
                        print(f"[+] Found flag? {fibon_str}")

            except IndexError:
                # fibonacci offset already overflows kipod_bytes
                # stop checking this byte
                break
    continue

img2bin.py

from PIL import Image

im = Image.open("dinary.png")
pix = im.load()

size = im.size
rows, cols = size
out = ""

for i in range(rows):
    for j in range(cols):
        r, g, b = pix[j, i]

        # print(f"pix[{i}, {j}] = [{r}, {g}, {b}]")
        if r > 122 and g > 122 and b > 122:
            out += "1"
        else:
            out += "0"


with open("out.txt", "w+") as out_file:
    out_file.write(out)

marker.py

import string

marked = []

with open("out.split.txt", "r+") as in_file:
    for line in in_file.readlines():
        line = line.strip("\n").strip(" ")
        char = int(line, 2)

        try:
            new_char = char.to_bytes(
                (char.bit_length() + 7) // 8, 'big'
            ).decode()
        except UnicodeDecodeError:
            new_char = ""

        new_line = ""
        if new_char == "" or new_char not in string.printable:
            new_line = line
        else:
            new_line = line + " # " + new_char

        marked.append(new_line)

with open("out.marked.txt", "w+") as out_file:
    out_file.write("\n".join(marked))