# Light SaBer solve

### There are only two pictures in the file.


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### Use HxD to open the help.png image and modify its height.


>## Get the picture below, which says ASCII CODE.
>

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### Use stegsolve to open and check the image.


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>## You can find that Blue Plane 0 seems to have a missing qrcode.
>

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### Save the image, splice the Qrcode and scan it to get a URL.


> ## https://webtes.onrender.com/

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### Go to the website and you will see an interface where you can upload files and enter messages.

### Try to upload the image and use stegsolve to check the returned image.



> ## Get the picture below
>

### Found that some pixels were changed


### It is speculated that LSB steganography using ascii code is used to send three different color images for checking.

>## etect B channel
>

>## etect R channel
>

>## etect G channel
>

> ## Presumably using the G 'green' channel

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### Write a script to check the modified pixel coordinate position of the image and record it

from PIL import Image
import numpy as np

image_path_1 = r"C:\Users\Maxsu\OneDrive\桌面\image1.png"
image_path_2 = r"C:\Users\Maxsu\OneDrive\桌面\image2.png"

def compare_images_and_print(image_path_1, image_path_2):
    # Load the images
    image1 = Image.open(image_path_1)
    image2 = Image.open(image_path_2)

    # Convert images to numpy arrays
    array1 = np.array(image1)
    array2 = np.array(image2)

    # Check if both images have the same size
    if array1.shape != array2.shape:
        raise ValueError("Images do not have the same size")

    # Find the pixels that are different
    diff = array1 != array2
    diff_coords = np.where(diff)

    if np.any(diff):  # If there are any differences
        # Extract the modified pixel values from both images
        modified_pixels_image1 = array1[diff_coords]
        modified_pixels_image2 = array2[diff_coords]

        # Prepare the data to be printed
        differences = list(zip(zip(*diff_coords), modified_pixels_image1, modified_pixels_image2))

        # Define a custom sorting function based on y, then x values
        def custom_sort(item):
            coords, orig_pixel, mod_pixel = item
            return (coords[1], coords[0])  # Sort by y first, then x

        # Sort the differences list using the custom sorting function
        differences.sort(key=custom_sort)

        # Print the differences
        for coords, orig_pixel, mod_pixel in differences:
            print(f"Coordinates: {coords}, Original: {orig_pixel}, Modified: {mod_pixel}")
    else:  # If the images are the same
        print("圖片相同")

# Run the comparison and catch any exceptions
try:
    compare_images_and_print(image_path_1, image_path_2)
except ValueError as e:
    print(e)

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#### Presumed to be ascii code conversion, use ÿ character to test the website
#### Enter messages of different lengths and you will find that up to 24 pixels will be modified.


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>## Can detect up to three steganographic characters and record their coordinate sequence
>first character(57, 57), (58, 8), (63, 54), (94, 46), (96, 160),(135, 88), (138, 110), (157, 169)
>second character(4, 184), (6, 59),(25, 0), (63, 178), (84, 90), (144, 177), (145, 123),(149, 91)
>third character (40, 56), (55, 153), (101, 157), (108, 9),
(131, 55), (134, 115), (186, 153), (194, 36)

### According to the rules obtained from the records, it is found that ascii code is used
### Use record coordinates to write a script to decrypt flag.png

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from PIL import Image

def lsb_decrypt_print_ascii_and_message(image_path, coordinates):
    try:
        # Load the image for decoding
        image = Image.open(image_path)
        pixels = image.load()

        # Retrieve the binary bits from the image's LSB of the green channel
        binary_bits = ''
        for coord in coordinates:
            x, y = coord
            pixel = list(pixels[x, y])
            # Extract the LSB of the green channel
            binary_bits += str(pixel[1] & 1)

        # Chunk the binary string into bytes of 8 bits
        binary_chunks = [binary_bits[i:i+8] for i in range(0, len(binary_bits), 8)]
        
        # Convert binary bytes to ASCII codes
        ascii_codes = [int(binary, 2) for binary in binary_chunks]
        # Convert binary bytes to ASCII characters
        message = ''.join([chr(code) for code in ascii_codes])
        
        # Print out the ASCII codes and the message
        print("ASCII Codes:", ascii_codes)
        print("Decoded Message:", message)
        return ascii_codes, message
    except Exception as e:
        print(f"Error decoding image: {e}")
        return None, None

# Coordinates provided in the original script
coordinates = [
    (57, 57), (58, 8), (63, 54), (94, 46), (96, 160),
    (135, 88), (138, 110), (157, 169), (4, 184), (6, 59),
    (25, 0), (63, 178), (84, 90), (144, 177), (145, 123),
    (149, 91), (40, 56), (55, 153), (101, 157), (108, 9),
    (131, 55), (134, 115), (186, 153), (194, 36)
]

# Placeholder for the actual path to the image
# Make sure to replace this with the actual path where the image is stored on your computer
image_path = r"C:\Users\Maxsu\OneDrive\桌面\encoded_falg1 (2).PNG"

# Decrypt the message and print both ASCII codes and the decoded message
ascii_codes, message = lsb_decrypt_print_ascii_and_message(image_path, coordinates)

### get flag
MCDX{orz}