/// <summary>
/// Create a new TP file for use in stenography from a file.
/// </summary>
/// <param name="file">The location of the file.</param>
/// <param name="key">The key to use in encrypting the data file.</param>
public TP_File(string file, string key)
{
byte[] fileBytes = TP_Encrypt.Encrypt(File.ReadAllBytes(file), key);
string fileName = ShortFileName(file);
// Create the fixed size header
byte[] header = new byte[128];
int fileNameMaxLength = header.Length - 4 - 1 - 3;
// First 4 bytes are for the file length
header[0] = (byte)(fileBytes.Length >> 24);
header[1] = (byte)((fileBytes.Length >> 16) & 0xFF);
header[2] = (byte)((fileBytes.Length >> 8) & 0xFF);
header[3] = (byte)(fileBytes.Length & 0xFF);
// Next byte is for the file name length
header[4] = (byte)Math.Min(fileNameMaxLength, fileName.Length);
// Last 3 bytes for the signature code
header[header.Length - 3] = (byte)(SIGNATURE[0]);
header[header.Length - 2] = (byte)(SIGNATURE[1]);
header[header.Length - 1] = (byte)(SIGNATURE[2]);
// Save the file name
for (int i = 0; i < Math.Min(fileNameMaxLength, fileName.Length); i++)
{
header[5 + i] = (byte)(fileName.ToCharArray()[i]);
}
// Encrypt the header
header = TP_Encrypt.Encrypt(header, key);
// Make enough space for both the header and the file
byte[] allBytes = new byte[header.Length + fileBytes.Length + 1];
// Save the header to the data to be written to the image
for (int i = 0; i < header.Length; i++)
{
allBytes[i] = header[i];
}
// Save the file data
for (int i = 0; i < fileBytes.Length; i++)
{
allBytes[i + header.Length] = fileBytes[i];
}
bytes = allBytes;
PadFileBytes();
}
/// <summary>
/// Create a new Header decoder
/// </summary>
/// <param name="input">The byte array extracted from the image</param>
/// <param name="key">The key used to initially encrypt the data</param>
public TP_Header(byte[] input, string key)
{
Key = key;
// The header is 144 bytes encrypted, but only 128 bytes decrypted
if (input.Length > 144)
{
// Get just the bytes for the header from the data
byte[] headerPre = new byte[144];
for (int i = 0; i < headerPre.Length; i++)
{
headerPre[i] = input[i];
}
// Decrypt the header
byte[] header = TP_Encrypt.Decrypt(headerPre, key);
// See if the decrypted header is actually a header
// If IsValid is true, then the image most likely contains a hidden file
// There is only a 1 in 2^24 chance (about 0.00000006%) that this will falsely be true
IsValid = header[header.Length - 3] == TP_File.SIGNATURE[0] &&
header[header.Length - 2] == TP_File.SIGNATURE[1] &&
header[header.Length - 1] == TP_File.SIGNATURE[2];
if (IsValid)
{
// Get the length of the hidden file
FileLength = 0;
FileLength |= header[0] << 24;
FileLength |= header[1] << 16;
FileLength |= header[2] << 8;
FileLength |= header[3];
// Get the length of the file name
int length = (int)header[4];
FileName = "";
// Get the original file name
for (int i = 0; i < length; i++)
{
FileName += (char)header[i + 5];
}
}
}
else
{
IsValid = false;
}
}
/// <summary>
/// Save the file represented by this data object.
/// </summary>
/// <param name="location">The location to save the file.</param>
public void Save(string location)
{
byte[] data = GetFileBytes();
File.WriteAllBytes(location, TP_Encrypt.Decrypt(data, fileHeader.Key));
}
