steg.py

#Bitcoin steganography library, inserts a private key, wif by default into a named file by altering the LSB of the r
#in the rgb palette of the pixel.
#Hex bitcoin private key is 64 bytes (512 bits to hide)
#WIF bitcoin private key is 51 bytes (408 bits to hide) and easily importable into a wallet for sweeping..

__author__ = 'pete'
from bitcoin import *                      #probably just need encode_privkey() and random_key()
from PIL import Image

def create_wif_key( key):
        return encode_privkey(key, 'wif')

class Steg():                           #instantiate a class which allows steganography data in and out of im..
    #def __init__(self,):

    def encode(self, file,  data, output='output.png'):            #put data into image..default output image output.png
        self.im = Image.open(file)
        self.im_w, self.im_h = self.im.size
        self.rgb_im = self.im.convert('RGB')

        self.output = output
        self.data = data + sha256(data)[-4:]
        self.data = chr(len(self.data)) + self.data
        #print self.data, len(self.data)                      #append checksum and prepend str length byte for easy extraction..

        self.datalen = len(self.data)   #number of bytes
        self.bitcount = self.datalen * 8    #number of bits in bytestring to disguise
        s  = []

        for x in range(0,self.datalen):     #convert the data into an ascii bit list.
            p = bin(ord(self.data[x]))
            p = p.lstrip('-0b')
            while len(p) < 8:               #pad the zero's up to 8
                p = '0'+ p
            s.append(p)
        s = "".join(s)                  #list to string

        if self.bitcount < self.im_w:               #can fit the entire message in first row of pixels..
            for x in range(0,self.bitcount):
                r, g, b = self.rgb_im.getpixel((x,0))       #get the pixel in r,g,b form..
                r = r & 254                                 #and 11111110
                if s[x] == '1':
                    r = r | 1                               #or 00000001
                self.rgb_im.putpixel((x,0),(r,g,b))         #put the replaced pixel with LSB altered..

        self.rgb_im.save(self.output)

    def decode(self,file = 'output.png'):         #n=512 (64 hex * 8), n=408 (64 hex -> 51 wif * 8) extract private key from file..
        self.im = Image.open(file)
        self.im_w, self.im_h = self.im.size
        self.rgb_im = self.im.convert('RGB')

        j = 0
        p = ""

        for x in range(0,8):                        #get the string length byte out first..
            r, g, b = self.rgb_im.getpixel((x,0))
            p = p + str(r & 1)
            j += 1

        self.bytelength = int(p,2)
        t  = []

        for x in range(0,(self.bytelength)):     #convert the ascii bit string back to ascii integer string
            p=""
            for y in range(0,8):
                r, g, b = self.rgb_im.getpixel((j,0))
                p = p + str(r & 1)                  #and each r value with b 00000001 to extract the encode bit as a byte
                j += 1
            t.append(chr(int(p,2)))
        t = "".join(t)

        if sha256(t[:-4])[-4:] == t[-4:]:           #last four bytes of t is checksum. do sha256 up to that to ensure integrity
            return t[:-4]
        else:
            return t + ' failed checksum'