private void Generate_Click(object sender, RoutedEventArgs e)
{
if (e != null && sender != null)
{
((ListBoxItem)MyListView.ContainerFromElement((Button)sender)).IsSelected = true;
string secret = _addAccount.GetSecret(MyListView.SelectedItem as string);
lastSecret = secret;
((ListBoxItem)MyListView.ContainerFromElement((Button)sender)).IsSelected = false;
}
Console.WriteLine("SECRET=" + lastSecret);
byte[] key;
try
{
// Google send you base32 string you need to decode it before using it.
key = Base32.Base32Encoder.Decode(lastSecret);
}
catch (Exception)
{
return;
}
// T = (Current Unix time - T0) / X (RFC 6238)
// Here we get the current time, then we substract the unix epoch (1st January 1970) and we divide by the step
// T0 is unix's epoch it's the default value
// X is the step here 30 seconds. Like before we use the default value
byte[] message = BitConverter.GetBytes((Int64)Math.Floor((DateTime.Now.ToUniversalTime() - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalSeconds / 30.0));
int remain = (int)Math.Floor((DateTime.Now.ToUniversalTime() - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalSeconds % 30.0);
// Why ? Why is it in big endian !!! See 5.2 Description RFC 4226
message = message.Reverse().ToArray();
// We use HMAC-SHA-1 algorithm because HOTP is based on this algorithm
HMACSHA1 hmac = new HMACSHA1(key);
byte[] hash = hmac.ComputeHash(message);
// We extract the nibble (quartet) of the last char
int nibble = (hash[hash.Length - 1] & 0xf);
// We extract 4 bytes from byte array and we need to set the first bit to 0
int truncatedHash = (hash[nibble] & 0x7f) << 24 | (hash[nibble + 1] & 0xff) << 16 | (hash[nibble + 2] & 0xff) << 8 | (hash[nibble + 3] & 0xff);
// We get a 6 digit code
string code = (truncatedHash % 1000000).ToString();
// If needed we add '0' if the code doesn't have enough digit
while (code.Length < 6)
{
code = "0" + code;
}
Code.Text = code.ToString();
Progress.Value = remain;
remainTimer.Start();
}