/// <summary>
/// Generates a new HOTP code using the supplied HMAC generater, key, counter and
/// HOTP length.
/// </summary>
/// <param name="hmac">The HMAC algorithm to use</param>
/// <param name="secretKey">The secret key used in HMAC-ing the counter</param>
/// <param name="counter">The counter to use to generate a HOTP code for</param>
/// <param name="hotpLength">The required length of the generated HOTP code</param>
/// <returns>The generated HOTP code</returns>
/// <exception cref="System.ArgumentNullException">Thrown if hmac or secretKey is null</exception>
/// <exception cref="System.ArgumentException">Thrown if secretKey is empty or hotpLength is not a valid value</exception>
public static string Generate(byte[] secretKey, ulong counter, HMAC hmac, OneTimePasswordLength hotpLength)
{
#region Input validation
Insist.IsNotNull(hmac, "hmac");
Insist.IsNotNull(secretKey, "secretKey");
Insist.IsNotEmpty(secretKey, "secretKey");
Insist.IsDefined<OneTimePasswordLength>(hotpLength, "hotpLength");
#endregion
byte[] hashedCounter = HashCounter(hmac, secretKey, counter);
uint truncatedHash = DynamicTruncate(hashedCounter);
//Convert to string and preserve leading 0s
return GenerateHotpValue(truncatedHash, hotpLength).ToString("D" + (int)hotpLength);
}
/// <summary>
/// Generates a new one time password using the current datetime and default timestep
/// </summary>
/// <param name="secretKey">The secret key to use in the HMAC</param>
/// <param name="hmac">The hmac algorithm to use</param>
/// <param name="otpLength">The required legnth of the returned passcode</param>
/// <returns>A one time password code of the required size</returns>
/// <exception cref="System.ArgumentNullException">Thrown if hmac or secret key is null</exception>
/// <exception cref="System.ArgumentException">Thrown if secret key is empty, optLength is
/// not defined value.</exception>
public static string Generate(byte[] secretKey, HMAC hmac, OneTimePasswordLength otpLength)
{
return Generate(secretKey, hmac, DateTime.Now, TimeSpan.Zero, DEFAULT_TIME_STEP, otpLength);
}
/// <summary>
/// Generates a new one time password from the supplied data.
/// </summary>
/// <param name="secretKey">The secret key to use in the HMAC</param>
/// <param name="hmac">The hmac algorithm to use</param>
/// <param name="dt">The date and time to generate a code for</param>
/// <param name="offset">Any offsets that should be applied to the supplie date time</param>
/// <param name="timeStep">The timestep value to use to calculate the current step</param>
/// <param name="otpLength">The required legnth of the returned passcode</param>
/// <returns>A one time password code</returns>
/// <exception cref="System.ArgumentNullException">Thrown if hmac or secret key is null</exception>
/// <exception cref="System.ArgumentException">Thrown if secret key is empty, optLength is
/// not defined value or timeStep is less than 1 second.</exception>
public static string Generate(byte[] secretKey, HMAC hmac, DateTime dt, TimeSpan offset, TimeSpan timeStep, OneTimePasswordLength otpLength)
{
#region Input validation
Insist.IsNotNull(hmac, "hmac");
Insist.IsNotNull(secretKey, "secretKey");
Insist.IsNotEmpty(secretKey, "secretKey");
Insist.IsDefined<OneTimePasswordLength>(otpLength, "optLength");
Insist.IsAtLeast(timeStep.TotalSeconds, 1, "timeStep");
#endregion
dt = dt + offset;
ulong stepNumber = (ulong)Math.Floor((double)dt.ToUnixTime() / (double)timeStep.TotalSeconds);
return HmacOneTimePassword.Generate(secretKey, stepNumber, hmac, otpLength);
}
/// <summary>
/// Generates a new one time password from the current datetime
/// </summary>
/// <param name="secretKey">The secret key to use in the HMAC</param>
/// <param name="hmac">The hmac algorithm to use</param>
/// <param name="timeStep">The timestep value to use to calculate the current step</param>
/// <param name="otpLength">The required legnth of the returned passcode</param>
/// <returns>A one time password code of the required length</returns>
/// <exception cref="System.ArgumentNullException">Thrown if hmac or secret key is null</exception>
/// <exception cref="System.ArgumentException">Thrown if secret key is empty, optLength is
/// not defined value or timeStep is less than 1 second.</exception>
public static string Generate(byte[] secretKey, HMAC hmac, TimeSpan timeStep, OneTimePasswordLength otpLength)
{
return Generate(secretKey, hmac, DateTime.Now, TimeSpan.Zero, timeStep, otpLength);
}
/// <summary>
/// Generates the final HOTP value from the truncated value
/// </summary>
private static uint GenerateHotpValue(UInt32 truncatedHash, OneTimePasswordLength htopLength)
{
//calculate 10^(htopLength-1)
int calculatedModulo = 10;
htopLength = htopLength - 1;
for (int i = 0; i < (int)htopLength; i++)
{
calculatedModulo *= 10;
}
return (uint)(truncatedHash % calculatedModulo);
}
/// <summary>
/// Generates a new one time password using the current datetime and default timestep
/// </summary>
/// <param name="secretKey">The secret key to use in the HMAC</param>
/// <param name="hmac">The hmac algorithm to use</param>
/// <param name="otpLength">The required legnth of the returned passcode</param>
/// <returns>A one time password code of the required size</returns>
/// <exception cref="System.ArgumentNullException">Thrown if hmac or secret key is null</exception>
/// <exception cref="System.ArgumentException">Thrown if secret key is empty, optLength is
/// not defined value.</exception>
public static string Generate(byte[] secretKey, HMAC hmac, OneTimePasswordLength otpLength)
{
return(Generate(secretKey, hmac, DateTime.Now, TimeSpan.Zero, DEFAULT_TIME_STEP, otpLength));
}
/// <summary>
/// Generates a new one time password from the supplied data.
/// </summary>
/// <param name="secretKey">The secret key to use in the HMAC</param>
/// <param name="hmac">The hmac algorithm to use</param>
/// <param name="dt">The date and time to generate a code for</param>
/// <param name="offset">Any offsets that should be applied to the supplie date time</param>
/// <param name="timeStep">The timestep value to use to calculate the current step</param>
/// <param name="otpLength">The required legnth of the returned passcode</param>
/// <returns>A one time password code</returns>
/// <exception cref="System.ArgumentNullException">Thrown if hmac or secret key is null</exception>
/// <exception cref="System.ArgumentException">Thrown if secret key is empty, optLength is
/// not defined value or timeStep is less than 1 second.</exception>
public static string Generate(byte[] secretKey, HMAC hmac, DateTime dt, TimeSpan offset, TimeSpan timeStep, OneTimePasswordLength otpLength)
{
#region Input validation
Insist.IsNotNull(hmac, "hmac");
Insist.IsNotNull(secretKey, "secretKey");
Insist.IsNotEmpty(secretKey, "secretKey");
Insist.IsDefined <OneTimePasswordLength>(otpLength, "optLength");
Insist.IsAtLeast(timeStep.TotalSeconds, 1, "timeStep");
#endregion
dt = dt + offset;
ulong stepNumber = (ulong)Math.Floor((double)dt.ToUnixTime() / (double)timeStep.TotalSeconds);
return(HmacOneTimePassword.Generate(secretKey, stepNumber, hmac, otpLength));
}
/// <summary>
/// Generates a new one time password from the current datetime
/// </summary>
/// <param name="secretKey">The secret key to use in the HMAC</param>
/// <param name="hmac">The hmac algorithm to use</param>
/// <param name="timeStep">The timestep value to use to calculate the current step</param>
/// <param name="otpLength">The required legnth of the returned passcode</param>
/// <returns>A one time password code of the required length</returns>
/// <exception cref="System.ArgumentNullException">Thrown if hmac or secret key is null</exception>
/// <exception cref="System.ArgumentException">Thrown if secret key is empty, optLength is
/// not defined value or timeStep is less than 1 second.</exception>
public static string Generate(byte[] secretKey, HMAC hmac, TimeSpan timeStep, OneTimePasswordLength otpLength)
{
return(Generate(secretKey, hmac, DateTime.Now, TimeSpan.Zero, timeStep, otpLength));
}
