/// <summary>
/// First 8 rounds of encryption
/// </summary>
private void EncryptionRounds()
{
byte[] data = new byte[8];
//srcFileStream.Seek(startIndex, SeekOrigin.Begin);
sbyte bytesCount = (sbyte)SrcFileStream.Read(data, 0, 8);
if (bytesCount == -1)
{
return;
}
if (bytesCount < 8)
{
for (int i = bytesCount; i < 8; i++)
{
data[i] = 0;
}
}
//преобразование в 16 битные(2 байтные) блоки
ushort[] blocks = new ushort[4];
for (int i = 0; i < 4; i++)
{
blocks[i] = BitConverter.ToUInt16(data, i * 2);
}
//раунды шифрования
for (int i = 0; i < 48; i += 6)
{
EncryptionRound(blocks, i);
}
EncryptionLastRound(blocks);
//преобразование обратно в байты
byte[] temp = null;
for (int i = 0; i < 8; i += 2)
{
temp = BitConverter.GetBytes(blocks[i / 2]);
data[i] = temp[0];
data[i + 1] = temp[1];
}
////запись в файл
//if (bytesCount < 8)
// resFileStream.Write(data, 0, bytesCount);
//else
ResFileStream.Write(data, 0, 8);
}
/// <summary>
/// Encrypt file with IDEA encryption
/// </summary>
public void Encrypt()
{
GenerateKeys();
var md5 = MD5.Create().ComputeHash(SrcFileStream);
CreateKeyFile(md5);
//запись MD5 хеша в зашифрованный файл
ResFileStream.Write(md5, 0, md5.Length);
//шифрование файла
SrcFileStream.Seek(0, SeekOrigin.Begin);
ResFileStream.WriteByte((byte)(8 - (SrcFileStream.Length % 8)));
for (long i = 0; i < SrcFileStream.Length; i += 8)
{
EncryptionRounds();
}
ResFileStream.Flush();
}
/// <summary>
/// Decrypt the file encrypted IDEA encryption
/// </summary>
/// <param name="SrcFileStream">Input file stream of the encrypted file</param>
/// <param name="ResFileStream">Output file stream of the decrypted file</param>
/// <param name="KeyFileStream">Input file stream of the key file</param>
public void Decrypt()
{
GenerateKey();
SrcFileStream.Seek(17, SeekOrigin.Begin);
ResFileStream.Seek(0, SeekOrigin.Begin);
for (long i = 17; i < SrcFileStream.Length; i += 8)
{
DecryptionRounds();
}
SrcFileStream.Seek(16, SeekOrigin.Begin);
byte offset = (byte)SrcFileStream.ReadByte();
if (!(offset == 8))
{
ResFileStream.SetLength(ResFileStream.Length - SrcFileStream.ReadByte());
}
ResFileStream.Flush();
}
