added steganography tutorial

Author: x4nth055

README.md

@@ -18,6 +18,7 @@ This is a repository of all the tutorials of [The Python Code](https://www.thepy
     - [How to Create a Reverse Shell in Python](https://www.thepythoncode.com/article/create-reverse-shell-python). ([code](ethical-hacking/reverse_shell))
     - [How to Encrypt and Decrypt Files in Python](https://www.thepythoncode.com/article/encrypt-decrypt-files-symmetric-python). ([code](ethical-hacking/file-encryption))
     - [How to Make a Subdomain Scanner in Python](https://www.thepythoncode.com/article/make-subdomain-scanner-python). ([code](ethical-hacking/subdomain-scanner))
+    - [How to use Steganography to Hide Secret Data in Images in Python](https://www.thepythoncode.com/article/hide-secret-data-in-images-using-steganography-python). ([code](ethical-hacking/steganography))
 
 - ### [Machine Learning](https://www.thepythoncode.com/topic/machine-learning)
     - ### [Natural Language Processing](https://www.thepythoncode.com/topic/nlp)

ethical-hacking/steganography/README.md

@@ -0,0 +1,15 @@
+# [How to use Steganography to Hide Secret Data in Images in Python](https://www.thepythoncode.com/article/hide-secret-data-in-images-using-steganography-python)
+To run this:
+- `pip3 install -r requimements.txt`
+- To encode some data to the imag `image.PNG` and decode it right away:
+    ```
+    python steganography image.PNG "This is some secret data."
+    ```
+    This will write another image with data encoded in it and **outputs:**
+    ```
+    [*] Maximum bytes to encode: 125028
+    [*] Encoding data...
+    [+] Decoding...
+    [+] Decoded data: This is some secret data.
+    ```
+- You can isolate encoding and decoding processes in two different Python files, which makes more sense.

ethical-hacking/steganography/encoded_image.PNG

@@ -0,0 +1,2 @@
+opencv-python
+numpy

ethical-hacking/steganography/image.PNG

@@ -0,0 +1,92 @@
+import cv2
+import numpy as np
+import sys
+
+
+def to_bin(data):
+    """Convert `data` to binary format as string"""
+    if isinstance(data, str):
+        return ''.join([ format(ord(i), "08b") for i in data ])
+    elif isinstance(data, bytes) or isinstance(data, np.ndarray):
+        return [ format(i, "08b") for i in data ]
+    elif isinstance(data, int) or isinstance(data, np.uint8):
+        return format(data, "08b")
+    else:
+        raise TypeError("Type not supported.")
+
+
+def encode(image_name, secret_data):
+    # read the image
+    image = cv2.imread(image_name)
+    # maximum bytes to encode
+    n_bytes = image.shape[0] * image.shape[1] * 3 // 8
+    print("[*] Maximum bytes to encode:", n_bytes)
+    if len(secret_data) > n_bytes:
+        raise ValueError("[!] Insufficient bytes, need bigger image or less data.")
+    print("[*] Encoding data...")
+    # add stopping criteria
+    secret_data += "====="
+    data_index = 0
+    # convert data to binary
+    binary_secret_data = to_bin(secret_data)
+    # size of data to hide
+    data_len = len(binary_secret_data)
+    
+    for row in image:
+        for pixel in row:
+            # convert RGB values to binary format
+            r, g, b = to_bin(pixel)
+            # modify the least significant bit only if there is still data to store
+            if data_index < data_len:
+                # least significant red pixel bit
+                pixel[0] = int(r[:-1] + binary_secret_data[data_index], 2)
+                data_index += 1
+            if data_index < data_len:
+                # least significant green pixel bit
+                pixel[1] = int(g[:-1] + binary_secret_data[data_index], 2)
+                data_index += 1
+            if data_index < data_len:
+                # least significant blue pixel bit
+                pixel[2] = int(b[:-1] + binary_secret_data[data_index], 2)
+                data_index += 1
+            # if data is encoded, just break out of the loop
+            if data_index >= data_len:
+                break
+    return image
+
+
+def decode(image_name):
+    print("[+] Decoding...")
+    # read the image
+    image = cv2.imread(image_name)
+    binary_data = ""
+    for row in image:
+        for pixel in row:
+            r, g, b = to_bin(pixel)
+            binary_data += r[-1]
+            binary_data += g[-1]
+            binary_data += b[-1]
+
+    # split by 8-bits
+    all_bytes = [ binary_data[i: i+8] for i in range(0, len(binary_data), 8) ]
+    # convert from bits to characters
+    decoded_data = ""
+    for byte in all_bytes:
+        decoded_data += chr(int(byte, 2))
+        if decoded_data[-5:] == "=====":
+            break
+    return decoded_data[:-5]
+
+
+if __name__ == "__main__":
+    input_image = sys.argv[1]
+    output_image = f"encoded_{input_image}"
+    secret_data = sys.argv[2]
+
+    # encode the data into the image
+    encoded_image = encode(image_name=input_image, secret_data=secret_data)
+    # save the output image (encoded image)
+    cv2.imwrite(output_image, encoded_image)
+    # decode the secret data from the image
+    decoded_data = decode(output_image)
+    print("[+] Decoded data:", decoded_data)