public byte[] hideMessage(string msg, string mykey, byte[] image, CryptoUtil.Algo algo)
{
if (msg == null || msg == "")
{
return(null);
}
byte[] key = null, iv = null, cipher = null;
(key, iv) = crypto.GetKeyIv(algo, mykey);
switch (algo)
{
case CryptoUtil.Algo.DES:
(key, iv, cipher) = crypto.EncryptDES(crypto.Zip(msg), key: key, iv: iv);
break;
default:
(key, iv, cipher) = crypto.EncryptAES(crypto.Zip(msg), key: key, iv: iv);
break;
}
using (var img = new Bitmap(new MemoryStream(image)))
{
var maxbytes = (img.Width * img.Height * 3) / 8 - 5;
if (cipher.Length > maxbytes)
{
return(null);
}
var binryArr = byteToBits(cipher);
int k = 0;
#region hide cipher using LSB
for (int i = 0; i < img.Width; i++)
{
for (int j = 0; j < img.Height; j++)
{
Color pixel = img.GetPixel(i, j);
byte r = pixel.R, g = pixel.G, b = pixel.B;
if (k < binryArr.Length)
{
r = binryArr[k] ? (byte)(r | 1) : (byte)(r & 254);
}
if (k + 1 < binryArr.Length)
{
g = binryArr[k + 1] ? (byte)(g | 1) : (byte)(g & 254);
}
if (k + 2 < binryArr.Length)
{
b = binryArr[k + 2] ? (byte)(b | 1) : (byte)(b & 254);
}
k += 3;
img.SetPixel(i, j, Color.FromArgb(r, g, b));
if (k >= binryArr.Length)
{
break;
}
}
if (k >= binryArr.Length)
{
break;
}
}
#endregion
#region total number of bytes saved
img.SetPixel(img.Width - 1, img.Height - 1,
Color.FromArgb((byte)(cipher.Length >> 16), (byte)(cipher.Length >> 8),
(byte)(cipher.Length)));
img.SetPixel(img.Width - 1, img.Height - 2,
Color.FromArgb(0, 0, (byte)(cipher.Length >> 24)));
#endregion
MemoryStream ms = new MemoryStream();
img.Save(ms, ImageFormat.Png);
byte[] bmpBytes = ms.ToArray();
return(bmpBytes);
#if DEBUGMODE
Console.WriteLine("cipher [{1}]: [{0}]", String.Join(",", cipher), cipher.Length);
printBinArr(binryArr);
Console.WriteLine(img.GetPixel(img.Width - 1, img.Height - 1));
Console.WriteLine(img.GetPixel(img.Width - 1, img.Height - 2));
Console.WriteLine(new String('-', 80));
#endif
}
//return true;
}
public string extractMessage(byte[] image, string mykey, CryptoUtil.Algo algo)
{
string msg = "";
byte[] key, iv;
(key, iv) = crypto.GetKeyIv(algo, mykey);
using (var img = new Bitmap(new MemoryStream(image)))
{
Color last1 = img.GetPixel(img.Width - 1, img.Height - 1),
last2 = img.GetPixel(img.Width - 1, img.Height - 2);
int msgSize = BitConverter.ToInt32(
new byte[] { last1.B, last1.G, last1.R, last2.B },
0);
var maxbytes = (img.Width * img.Height * 3) / 8 - 5;
if (msgSize > maxbytes || msgSize <= 0)
{
return("");
}
var binryArr = new bool[msgSize * 8];
int k = 0;
#region extract cipher using LSB
for (int i = 0; i < img.Width; i++)
{
for (int j = 0; j < img.Height; j++)
{
Color pixel = img.GetPixel(i, j);
byte r = pixel.R, g = pixel.G, b = pixel.B;
if (k < binryArr.Length)
{
binryArr[k] = (r & 1) == 1;
}
if (k + 1 < binryArr.Length)
{
binryArr[k + 1] = (g & 1) == 1;
}
if (k + 2 < binryArr.Length)
{
binryArr[k + 2] = (b & 1) == 1;
}
k += 3;
if (k >= binryArr.Length)
{
break;
}
}
if (k >= binryArr.Length)
{
break;
}
}
#endregion
byte[] cipher = bitsToByte(binryArr);
byte[] decrypted = null;
switch (algo)
{
case CryptoUtil.Algo.DES:
decrypted = crypto.DecryptDES(cipher, key, iv);
break;
default:
decrypted = crypto.DecryptAES(cipher, key, iv);
break;
}
try
{
msg = crypto.Unzip(decrypted);
}
catch (Exception)
{
return("");
}
#if DEBUGMODE
Console.WriteLine(last1);
Console.WriteLine(last2);
Console.WriteLine(msgSize);
printBinArr(binryArr);
Console.WriteLine("cipher : [{0}]", String.Join(",", cipher));
#endif
}
return(msg);
}
