Adds steganography scripts and image to static

flags/steganography/decode.py

+from PIL import Image
+import sys
+import types
+
+def frombits(bits):
+    chars = []
+    for b in range(len(bits) / 8):
+        byte = bits[b*8:(b+1)*8]
+        chars.append(chr(int(''.join([str(bit) for bit in byte]), 2)))
+    return ''.join(chars)
+
+def decode_message(pixel):
+    if type(pixel) is types.IntType:
+        return "{0:02b}".format(pixel%4)
+    #RGB
+    if type(pixel) is types.TupleType:
+        R, G, B = pixel
+        if R >= G and R >= B:
+            return  "{0:02b}".format(R%4)
+        if G >= R and G >= B:
+            return  "{0:02b}".format(G%4)
+        if B >= G and B >= R:
+            return  "{0:02b}".format(B%4)
+
+IMAGE_PATH = "./stegano.bmp"
+
+im = Image.open(IMAGE_PATH)
+
+pixels = im.load()
+
+width, height = im.size
+
+extracted_msg = ""
+
+for x in range(0,width):
+    for y in range(0,height):
+        extracted_msg = extracted_msg + decode_message(pixels[x,y])
+
+message = frombits(extracted_msg)
+
+print (message)

flags/steganography/encode.py

+from PIL import Image
+import sys
+import types
+
+def tobits(s):
+    result = []
+    for c in s:
+        bits = bin(ord(c))[2:]
+        bits = '00000000'[len(bits):] + bits
+        result.extend([int(b) for b in bits])
+    return result
+
+def frombits(bits):
+    chars = []
+    for b in range(len(bits) / 8):
+        byte = bits[b*8:(b+1)*8]
+        chars.append(chr(int(''.join([str(bit) for bit in byte]), 2)))
+    return ''.join(chars)
+
+def clear_last_two_bits(num):
+    #black and white
+    if type(num) is types.IntType:
+        return num - (num % 4)
+    #RGB
+    if type(num) is types.TupleType:
+        R, G, B = num
+        return (R - (R % 4),G - (G % 4),B - (B % 4))
+
+def encode_message(pixel, message):
+    msg = 2 * message[0] + message[1]
+
+    #black and white
+    if type(pixel) is types.IntType:
+        return pixel + msg
+    #RGB
+    if type(pixel) is types.TupleType:
+        R, G, B = pixel
+        if R >= G and R >= B:
+            return (R + msg, G, B)
+        if G >= R and G >= B:
+            return (R, G + msg, B)
+        if B >= G and B >= R:
+            return (R, G, B + msg)
+
+
+def decode_message(pixel):
+    if type(pixel) is types.IntType:
+        return "{0:02b}".format(pixel%4)
+    #RGB
+    if type(pixel) is types.TupleType:
+        R, G, B = pixel
+        if R >= G and R >= B:
+            return  "{0:02b}".format(R%4)
+        if G >= R and G >= B:
+            return  "{0:02b}".format(G%4)
+        if B >= G and B >= R:
+            return  "{0:02b}".format(B%4)
+
+IMAGE_PATH = "./stegano.bmp"
+MESSAGE = "KYN_2016_Steganography"
+MESG_SIZE = sys.getsizeof(MESSAGE)
+encoding = 'utf-8'
+
+im = Image.open(IMAGE_PATH)
+
+pixels = im.load()
+
+width, height = im.size
+
+number_of_pixels = width * height
+number_of_bytes = (number_of_pixels * 4) / 8
+if MESG_SIZE > number_of_bytes:
+    print ("Image too small for the message")
+
+message = tobits(MESSAGE)
+
+length = len(message)
+
+extracted_msg = ""
+
+for x in range(0,width):
+    for y in range(0,height):
+        bits_encoded = 2 *(x*height + y)
+        if bits_encoded < len(message):
+            sub_message = message[bits_encoded:bits_encoded + 2]
+        else:
+            sub_message = 2*[0]
+
+        pixels[x,y] = clear_last_two_bits(pixels[x,y])
+        pixels[x,y] = encode_message(pixels[x,y], sub_message)
+
+
+for x in range(0,width):
+    for y in range(0,height):
+        extracted_msg = extracted_msg + decode_message(pixels[x,y])
+
+im.save('./stegano2.bmp')
+
+message_str = frombits(message)
+message2 = frombits(extracted_msg)
+
+print (message_str)
+print (message2)