358 lines
14 KiB
Python
358 lines
14 KiB
Python
'''
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For each color channel of each pixel in an Image, modify the least significant bit to represent a bit of the Secret file.
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This changes the RGB value of the pixel by a usually-imperceptible amount.
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The first 32 bits (10.66 pixels) will be used to store the length of the Secret content in big endian.
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Then, the Secret's extension is stored. A null byte indicates the end of the extension. This section is of variable length.
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A file with no extension requires only that null byte. A file with an extension requires 1 additional byte per character.
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Smallest image possible = 16 pixels with 48 bit secret: 32 for header; 8 for null extension; 8 for data.
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Each Image pixel holds 3 Secret bits, so the Image must have at least ((secretbytes * (8 / 3)) + 14) pixels.
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An Image can hold ((3 * (pixels - 14)) / 8) Secret bytes.
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Usage:
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> steganographic.py encode imagefilename.png secretfilename.ext
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> steganographic.py decode lacedimagename.png
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Reference table for files with NO EXTENSION.
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For each extension character, subtract 1 byte from secret size
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pixels | example dimensions | Secret file size
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100 | 10 x 10 | 32 bytes
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400 | 20 x 20 | 144 bytes
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2,500 | 50 x 50 | 932 bytes
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10,000 | 100 x 100 | 3,744 bytes
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40,000 | 200 x 200 | 14,994 bytes
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25,000 | 500 x 500 | 93,744 bytes (91 kb)
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1,000,000 | 1,000 x 1,000 | 374,994 bytes (366 kb)
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4,000,000 | 2,000 x 2,000 | 1,499,994 bytes (1.43 mb)
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25,000,000 | 5,000 x 5,000 | 9,374,994 bytes (8.94 mb)
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100,000,000 | 10,000 x 10,000 | 37,499,994 bytes (35.7 mb)
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pixels | example dimensions | Secret file size
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100 | 10 x 10 | 32 bytes
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697 | 25 x 28 (700) | 256 bytes
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2,745 | 50 x 55 (2,750) | 1,024 bytes (1 kb)
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21,860 | 142 x 154 (21,868) | 8,192 bytes (8 kb)
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87,396 | 230 x 380 (87,400) | 32,768 bytes (32 kb)
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349,540 | 463 x 755 (349,565) | 131,072 bytes (128 kb)
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1,398,116 | 1146 x 1120 (1,398,120) | 524,288 bytes (512 kb)
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2,796,217 | 1621 x 1725 (2,796,225) | 1,048,576 bytes (1 mb)
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11,184,825 | 3500 x 3200 (11,200,000) | 4,194,304 bytes (4 mb)
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44,739,257 | 6700 x 6700 (44,890,000) | 16,777,216 bytes (16 mb)
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89,478,500 | 9500 x 9500 (90,250,000) | 33,554,432 bytes (32 mb)
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'''
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from PIL import Image
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import binascii
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import math
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import os
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import sys
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# 11 pixels for the secret file size
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HEADER_SIZE = 11
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FILE_READ_SIZE = 4 * 1024
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class StegError(Exception):
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pass
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class BitsToImage:
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def __init__(self, image, bitness):
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self.image = image
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self.bitness = bitness
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self.width = image.size[0]
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self.pixel_index = -1
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self.channel_index = 0
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self.bit_index = self.bitness - 1
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self.active_pixel = None
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self.x = 0
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self.y = 0
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def _write(self, bit):
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if self.active_pixel is None:
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self.pixel_index += 1
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self.channel_index = 0
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self.bit_index = self.bitness - 1
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(self.x, self.y) = index_to_xy(self.pixel_index, self.width)
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self.active_pixel = list(self.image.getpixel((self.x, self.y)))
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channel = self.active_pixel[self.channel_index]
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channel = set_bit(channel, self.bit_index, int(bit))
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self.active_pixel[self.channel_index] = channel
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self.bit_index -= 1
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if self.bit_index < 0:
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# We have exhausted our bitness for this channel.
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self.bit_index = self.bitness - 1
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self.channel_index += 1
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if self.channel_index == 3:
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# We have exhausted the channels for this pixel.
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self.image.putpixel((self.x, self.y), tuple(self.active_pixel))
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self.active_pixel = None
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def write(self, bits):
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for bit in bits:
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self._write(bit)
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class ImageToBits:
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def __init__(self, image, bitness):
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self.image = image
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self.bitness = bitness
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self.width = image.size[0]
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self.height = image.size[1]
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self.pixel_index = -1
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self.bit_index = bitness
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self.active_byte = []
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self.pixels = self.image.getdata()
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#self.bits = ''
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#for pixel in self.pixels:
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# for channel in pixel:
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# self.bits += binary(channel)[-bitness:]
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#print(len(self.bits))
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def _read(self):
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if len(self.active_byte) == 0:
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self.pixel_index += 1
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self.active_byte = self.pixels[self.pixel_index]
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self.active_byte = self.active_byte[:3]
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self.active_byte = [binary(channel) for channel in self.active_byte]
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self.active_byte = [channel[-bitness:] for channel in self.active_byte]
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self.active_byte = ''.join(self.active_byte)
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self.active_byte = list(self.active_byte)
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ret = self.active_byte.pop(0)
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self.bit_index += 1
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return ret
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def read(self, bits=1):
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return ''.join(self._read() for x in range(bits))
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def binary(i):
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return bin(i)[2:].rjust(8, '0')
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def chunk_iterable(iterable, chunk_length, allow_incomplete=True):
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'''
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Given an iterable, divide it into chunks of length `chunk_length`.
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If `allow_incomplete` is True, the final element of the returned list may be shorter
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than `chunk_length`. If it is False, those items are discarded.
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'''
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if len(iterable) % chunk_length != 0 and allow_incomplete:
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overflow = 1
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else:
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overflow = 0
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steps = (len(iterable) // chunk_length) + overflow
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return [iterable[chunk_length * x : (chunk_length * x) + chunk_length] for x in range(steps)]
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def index_to_xy(index, width):
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x = index % width
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y = index // width
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return (x, y)
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def bytes_to_pixels(bytes):
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return ((bytes * (8 / 3)) + 14)
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def pixels_to_bytes(pixels):
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return ((3 * (pixels - 14)) / 8)
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def set_bit(number, index, newvalue):
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# Thanks unwind
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# http://stackoverflow.com/a/12174051/5430534
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mask = 1 << index
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number &= ~mask
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if newvalue:
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number |= mask
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return number
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############## #### #### ######## ###### ########## ##############
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#### ## #### #### #### #### #### #### #### #### #### ##
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#### ###### #### #### #### #### #### #### #### ####
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#### ## ######## #### #### #### #### #### #### #### ##
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########## ############## #### #### #### #### #### ##########
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#### ## #### ######## #### #### #### #### #### #### ##
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#### #### ###### #### #### #### #### #### #### ####
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#### ## #### #### #### #### #### #### #### #### #### ##
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############## #### #### ######## ###### ########## ##############
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def encode(imagefilename, secretfilename, bitness=1):
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pixel_index = 0
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channel_index = 0
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if bitness < 1:
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raise ValueError('Cannot modify less than 1 bit per channel')
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if bitness > 8:
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raise ValueError('Cannot modify more than 8 bits per channel')
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print('Hiding "%s" within "%s"' % (secretfilename, imagefilename))
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secret_size = os.path.getsize(secretfilename)
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if secret_size == 0:
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raise StegError('The Secret can\'t be 0 bytes.')
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image = Image.open(imagefilename)
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image_steg = BitsToImage(image, bitness)
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total_pixels = image.size[0] * image.size[1]
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if total_pixels < HEADER_SIZE:
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raise StegError('Image cannot have fewer than %d pixels. They are used to store Secret\'s length' % HEADER_SIZE)
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secret_extension = os.path.splitext(secretfilename)[1][1:]
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secret_content_length = (secret_size) + (len(secret_extension)) + 1
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requiredpixels = math.ceil(((secret_content_length * 8) + 32) / (3 * bitness))
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if total_pixels < requiredpixels:
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raise StegError('Image does not have enough pixels to store the Secret. '
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'Must have at least %d pixels' % requiredpixels)
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print('%d pixels available, %d required' % (total_pixels, requiredpixels))
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# --> YOU ARE HERE <--
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pixel = list(image.getpixel((0, 0)))
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# Write secret length
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secret_content_length_b = binary(secret_content_length).rjust(32, '0')
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print('Content bytes:', secret_content_length)
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image_steg.write(secret_content_length_b)
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# Write the secret extension
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for character in (secret_extension + chr(0)):
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image_steg.write(binary(ord(character)))
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# Write the secret data
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bytes_written = 0
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one_complete_file = False
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# Yes, we're assuming the whole file fits in memory.
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secret_file = open(secretfilename, 'rb')
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secret_data = secret_file.read()
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secret_data_size = len(secret_data)
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secret_index = 0
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for pixel_number in range(total_pixels):
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if pixel_number % 4 == 0:
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#percentage = (bytes_written + 1) / secret_size
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#percentage = '%07.3f%%\r' % (100 * percentage)
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#print(percentage, end='')
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print(pixel_number)
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secret_chunk = secret_data[secret_index:secret_index+FILE_READ_SIZE]
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secret_index += FILE_READ_SIZE
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if len(secret_chunk) < FILE_READ_SIZE:
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one_complete_file = True
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#secret_index = 0
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rs = FILE_READ_SIZE - len(secret_chunk)
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secret_chunk += os.urandom(rs)
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#secret_chunk += secret_data[secret_index:secret_index+rs]
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secret_chunk = list(secret_chunk)
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secret_chunk = [binary(byte) for byte in secret_chunk]
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bytes_written += len(secret_chunk)
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secret_chunk = ''.join(secret_chunk)
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try:
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image_steg.write(secret_chunk)
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except IndexError:
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if one_complete_file:
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break
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else:
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raise
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# haha
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print('100.000%')
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if channel_index != 0:
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# The Secret data has finished, but we still have an unsaved pixel
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# (because channel_index is set to 0 when we save the active pixel above)
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(x, y) = index_to_xy(pixel_index, image.size[0])
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image.putpixel((x, y), tuple(pixel))
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new_name = os.path.splitext(imagefilename)[0]
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original_name = os.path.basename(secretfilename).replace('.', '_')
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newname = '%s (%s) (%d).png' % (new_name, original_name, bitness)
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print('Writing:', newname)
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image.save(newname)
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########## ############## ######## ###### ########## ##############
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#### #### #### ## #### #### #### #### #### #### #### ##
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#### #### #### #### #### #### #### #### #### ####
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#### #### #### ## #### #### #### #### #### #### ##
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#### #### ########## #### #### #### #### #### ##########
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#### #### #### ## #### #### #### #### #### #### ##
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#### #### #### #### #### #### #### #### #### ####
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#### #### #### ## #### #### #### #### #### #### #### ##
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########## ############## ######## ###### ########## ##############
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def decode(imagefilename, bitness=1):
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print('Extracting content from "%s"' % imagefilename)
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image = Image.open(imagefilename)
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image_steg = ImageToBits(image, bitness)
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# determine the content length
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content_length = image_steg.read(32)
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content_length = int(content_length, 2)
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print('Content bytes:', content_length)
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# determine secret extension
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extension = ''
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while extension[-8:] != '00000000' or len(extension) % 8 != 0:
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extension += image_steg.read()
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extension = chunk_iterable(extension, 8)
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extension.remove('00000000')
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extension = [chr(int(x, 2)) for x in extension]
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extension = ''.join(extension)
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print('Extension:', extension)
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# Remove the extension length, and null byte
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content_length -= 1
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content_length -= len(extension)
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# Prepare writes
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newname = os.path.splitext(imagefilename)[0]
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if extension != '':
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extension = '.' + extension
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newname = '%s (extracted)%s' % (newname, extension)
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outfile = open(newname, 'wb')
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# extract data
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bytes_written = 0
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while bytes_written < content_length:
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if bytes_written % 1024 == 0:
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percentage = (bytes_written + 1) / content_length
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percentage = '%07.3f%%\r' % (100 * percentage)
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print(percentage, end='')
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byte = image_steg.read(8)
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byte = '%02x' % int(byte, 2)
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outfile.write(binascii.a2b_hex(byte))
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bytes_written += 1
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# I'm on fire
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print('100.000%')
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print('Wrote', newname)
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outfile.close()
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def listget(li, index, fallback=None):
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try:
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return li[index]
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except IndexError:
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return fallback
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if __name__ == '__main__':
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command = listget(sys.argv, 1, '').lower()
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if command not in ['encode', 'decode']:
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print('Usage:')
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print('> steganographic.py encode imagefilename.png secretfilename.ext bitness')
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print('> steganographic.py decode lacedimagename.png bitness')
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quit()
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imagefilename = sys.argv[2]
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if command == 'encode':
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secretfilename = sys.argv[3]
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bitness = int(sys.argv[4])
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encode(imagefilename, secretfilename, bitness)
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else:
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bitness = int(sys.argv[3])
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decode(imagefilename, bitness) |