public Bitmap HideData(string content, string secretKey)
{
if (!Readable())
{
throw new ApplicationException("Unable to read from this image.");
}
string inputKey = null;
var contentToWrite = Encoding.UTF8.GetBytes(content);
if (!string.IsNullOrEmpty(secretKey))
{
//Starts a new rjindael input key
inputKey = Guid.NewGuid().ToString().Replace("-", "");
var encryptedString = RjindaelHelper.EncryptRijndael(content, secretKey, inputKey);
contentToWrite = Convert.FromBase64String(encryptedString);
}
var capacity = BitCapacity();
int size = contentToWrite.Length;
byte[] sizeToBytes = BitConverter.GetBytes(size);
var contentSize = contentToWrite.Length + (sizeToBytes.Length * 8);
if (!string.IsNullOrEmpty(secretKey))
{
contentSize = contentSize + 256;
}
if (contentSize > capacity)
{
throw new ApplicationException("Content is too big to hide on this image.");
}
var package = new List <byte>();
package.AddRange(sizeToBytes);
if (inputKey != null)
{
var inputKeyToASCIIBytes = Encoding.ASCII.GetBytes(inputKey);
package.AddRange(inputKeyToASCIIBytes);
}
package.AddRange(contentToWrite);
var bitsToWrite = new BitArray(package.ToArray());
int bitIndex = 0;
_output.WriteLine($"Hiding {contentToWrite.Length * 8} bits...");
var output = new Bitmap(Image.FromStream(_contentStream));
int R = 0, G = 0, B = 0;
_output.WriteLine($"Writing data...");
//Loop again but write the data on the clean pixels
for (int y = 0; y < output.Height; y++)
{
if (bitIndex >= bitsToWrite.Count)
{
break;
}
for (int x = 0; x < output.Width; x++)
{
if (bitIndex >= bitsToWrite.Count)
{
break;
}
Color pixel = output.GetPixel(x, y);
//Set the next 3 bits to write
var next3bits = new BitArray(new bool[] { false, false, false });
for (var index = 0; index < next3bits.Count; index++)
{
if (bitIndex >= bitsToWrite.Count)
{
continue;
}
next3bits[index] = bitsToWrite.Get(bitIndex);
bitIndex++;
}
//Remove the least significant bit value
R = pixel.R - pixel.R % 2;
G = pixel.G - pixel.G % 2;
B = pixel.B - pixel.B % 2;
//Apply the actual data
R = R + Convert.ToByte(next3bits[0]);
G = G + Convert.ToByte(next3bits[1]);
B = B + Convert.ToByte(next3bits[2]);
output.SetPixel(x, y, Color.FromArgb(R, G, B));
}
}
return(output);
}
public static string ReadData(Bitmap bitmap, string secretKey)
{
var bitList = new List <bool>();
var ended = false;
for (int y = 0; y < bitmap.Height; y++)
{
if (ended)
{
break;
}
for (int x = 0; x < bitmap.Width; x++)
{
if (ended)
{
break;
}
var pixel = bitmap.GetPixel(x, y);
var bit1 = Convert.ToBoolean(pixel.R % 2);
var bit2 = Convert.ToBoolean(pixel.G % 2);
var bit3 = Convert.ToBoolean(pixel.B % 2);
bitList.Add(bit1);
bitList.Add(bit2);
bitList.Add(bit3);
}
}
var startIndex = 32;
var sizeBitArray = new BitArray(bitList.GetRange(0, 32).ToArray());
var outputSizeBytes = new byte[4];
sizeBitArray.CopyTo(outputSizeBytes, 0);
var outputSize = BitConverter.ToInt32(outputSizeBytes);
Console.WriteLine($"Output size: {outputSize * 8} bits");
string inputKey = null;
if (!string.IsNullOrEmpty(secretKey))
{
startIndex = startIndex + 256;
var inputKeyBitArray = new BitArray(bitList.GetRange(32, 256).ToArray());
var outputSizeInputKeyBytes = new byte[32];
inputKeyBitArray.CopyTo(outputSizeInputKeyBytes, 0);
inputKey = Encoding.ASCII.GetString(outputSizeInputKeyBytes).Trim();
}
bitList = bitList.GetRange(startIndex, (outputSize * 8));
var outputArray = new BitArray(bitList.ToArray());
if (outputArray.Count % 8 != 0)
{
throw new ApplicationException($"Invalid number of bits: {outputArray.Count}.");
}
var bytes = new byte[outputArray.Count / 8];
outputArray.CopyTo(bytes, 0);
string outputString = null;
if (inputKey != null)
{
outputString = Convert.ToBase64String(bytes);
outputString = RjindaelHelper.DecryptRijndael(outputString, secretKey, inputKey);
}
else
{
outputString = Encoding.UTF8.GetString(bytes);
}
return(outputString);
}
