public static AuthCode GenerateAuthCode(AuthKey key)
{
if (key.Type == AuthType.HOTP)
return GenerateHOTP(key, key.Counter);
return GenerateTOTP(key, DateTime.UtcNow);
}
public static AuthCode GenerateTOTP(AuthKey key, DateTime dateTime)
{
long T = getTfromTime(dateTime, key.Period);
var authCode = GenerateHOTP(key, T);
authCode.Age = getAgeFromTime(dateTime, key.Period);
return authCode;
}
private static AuthCode GenerateHOTP(AuthKey key, long C)
{
byte[] Cbytes = getBytesFromLong(C);
HMAC hmac = HMAC.Create("HMAC" + key.Algorithm);
hmac.Key = key.Key;
byte[] hash = hmac.ComputeHash(Cbytes);
// put selected bytes into result int
int offset = hash[hash.Length - 1] & 0xf;
int binary = ((hash[offset] & 0x7f) << 24) | (hash[offset + 1] << 16) | (hash[offset + 2] << 8) | hash[offset + 3];
int otp = binary % DIGITS_POWER[key.NumDigits];
string totpString = Convert.ToString(otp);
while (totpString.Length < key.NumDigits)
totpString = "0" + totpString;
return new AuthCode { Value = totpString };
}
public AuthorizerEntry(string uriString)
{
this.authKey = new AuthKey(uriString);
initializeGuiElements();
UpdateCodeAsync();
}