/// <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));
}