Authenticator token generation

gistfile1.cpp

/// <summary>
/// 10^0..10^8 (NumDigits used in the HOTP)
/// </summary>
private static readonly int[] DigitsPower = {1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000};

private static int DynamicTruncate(byte[] hash)
{
    int offset = hash[hash.Length - 1] & 15;

    return ((hash[offset] & 127) << 24) + ((hash[offset + 1] & 255) << 16) + ((hash[offset + 2] & 255) << 8) +
            (hash[offset + 3] & 255);
}

public string GenerateCode()
{
    long time = (BlizzTime/30000);

    byte[] timeBytes = BitConverter.GetBytes(time);
    // Invert the endian-ness, giving us a big endian number
    Array.Reverse(timeBytes);

    var sha1 = new HMACSHA1(Token); // Secret Token

    byte[] h = sha1.ComputeHash(timeBytes);
    int code = DynamicTruncate(h)%DigitsPower[8];

    return code.ToString().PadLeft(8, '0');
}