public void EncryptSerial(byte[] info, byte[] firmware)
{
//Calculate the checksum and the CRC16 of the info block before the encryption.
//Fill the empty info arrary with random values.
for (int i = 32; i < info.Length - 2; i++)
{
info[i] = (byte)Utils.Generator.Next(0, 255);
}
//compute the 8Bit checksum of devcode and serial string and store it in the position 34.
byte cs = 0;
for (int i = 5; i < 34; i++)
{
cs += info[i];
}
info[34] = cs;
//compute the CRC16 of the info array and store it in the last two position in little endian order.
ushort crc;
CRC16 crc16 = new CRC16();
crc = crc16.GetCRC16(info, info.Length - 2, 0);
info[info.Length - 1] = (byte)((crc >> 8));
info[info.Length - 2] = (byte)(crc & 0xFF);
//Now we encrypt the info block, ready to be inserted in the firmware.
/*Step1
* Data scrambling. We swap the first byte with the last, the fourth from the beginning with the fourth from the end and so on.
* So we have the following 10 swaps:(0-79),(4-75),(8-71),(12-67),(16-63),(20-59),(24-55),(28-51),(32-47),(36-43).
*/
for (int i = 0; i < info.Length / 2; i += 4)
{
byte t = info[i];
info[i] = info[info.Length - i - 1];
info[info.Length - i - 1] = t;
}
//Step 2, Left rotate the whole array by 3 bits.
byte m = (byte)(info[0] >> 5);
for (int i = 0; i < info.Length - 1; i++)
{
info[i] = (byte)(info[i] << 3 & 0xF8 | info[i + 1] >> 5);
}
info[info.Length - 1] = (byte)(info[info.Length - 1] << 3 & 0xF8 | m);
//step3 xoring each info table value with a random number from xortable. The start index in this table is 0x0A. Index is incremented modulo 256
byte index = 0x0A;
for (int i = 0; i < info.Length; i++)
{
info[i] = (byte)(info[i] ^ firmware[XOR_TABLE_OFFSET + index++]);
}
}
private ushort GetKeyCRC(byte[] data)
{
CRC16 crc16 = new CRC16();
return(crc16.GetCRC16(data, 0));
}
ushort get_dev_crc()
{
CRC16 crc16 = new CRC16();
return(crc16.GetCRC16(Encoding.ASCII.GetBytes(TxtDevcode.Text), TxtDevcode.Text.Length, 0));
}