ساخت کد Time-based one time password همراه با زمان انقضای آن

private static ulong GetCurrentTimeStepNumber()
{
#if NETSTANDARD2_0 || NET461
    var delta = DateTime.UtcNow - _unixEpoch;
#else
    var delta = DateTimeOffset.UtcNow - DateTimeOffset.UnixEpoch;
#endif
    return (ulong)(delta.Ticks / _timestep.Ticks);
}

public static bool ValidateCode(byte[] securityToken, int code, string modifier = null)
{
    if (securityToken == null)
    {
        throw new ArgumentNullException(nameof(securityToken));
    }

    // Allow a variance of no greater than 9 minutes in either direction
    var currentTimeStep = GetCurrentTimeStepNumber();
    using (var hashAlgorithm = new HMACSHA1(securityToken))
    {
        for (var i = -2; i <= 2; i++)
        {
            var computedTotp = ComputeTotp(hashAlgorithm, (ulong)((long)currentTimeStep + i), modifier);
            if (computedTotp == code)
            {
                return true;
            }
        }
    }

    // No match
    return false;
}

public static bool ValidateCode(
    string securityStampToken,
    int code,
    string modifier,
    int expirationInMinutes)
{
    if (securityStampToken == null)
    {
        throw new ArgumentNullException(nameof(securityStampToken));
    }

    byte[] securityTokenBytes = GetBytes(securityStampToken);

    using (var hashAlgorithm = new HMACSHA1(securityTokenBytes))
    {
        for (var i = -Math.Abs(expirationInMinutes); i <= 1; i++)
        {
            var currentTimeStep = GetNextTimeStepNumber(i);

            var computedTotp = ComputeTotp(hashAlgorithm, (ulong)((long)currentTimeStep), modifier);
            if (computedTotp == code)
            {
                return true;
            }
        }
    }

    // No match
    return false;
}

Totp:1:TwoFactorActivation

public async ValueTask<bool> ValidateTwoFactorTotpCode(string email, int totpCode)
{
    var user = await GetUserByEmail(email);

    string modifier = GetModifier(user, TotpEnum.TwoFactor);

    var isValid = TotpService.ValidateCode(
        user.SecurityStamp.ToString(),
        totpCode,
        modifier,
        _userOption.TwoFactorTotpExpiration);

    return isValid;
}

//Generate totp code
var totpCode = TotpService.GenerateCode(user.SecurityStamp.ToString(), modifier);

//Verify totp code
var isValid = TotpService.ValidateCode(
    user.SecurityStamp.ToString(), 
    totpCode, 
    modifier, 
    _userOption.TwoFactorTotpExpiration);

public override async Task<string> GenerateAsync(
    string purpose,
    UserManager<ApplicationUser> manager,
    ApplicationUser user)
{
    if (manager == null)
    {
        throw new ArgumentNullException(nameof(manager));
    }
    var token = await manager.CreateSecurityTokenAsync(user);
    var modifier = await GetUserModifierAsync(purpose, manager, user);

    return TotpService.GenerateCode(token, modifier).ToString("D6", CultureInfo.InvariantCulture);
}

public override async Task<bool> ValidateAsync(
    string purpose,
    string token,
    UserManager<ApplicationUser> manager,
    ApplicationUser user)
{
    if (manager == null)
    {
        throw new ArgumentNullException(nameof(manager));
    }
    int code;
    if (!int.TryParse(token, out code))
    {
        return false;
    }
    var securityToken = await manager.CreateSecurityTokenAsync(user);
    var modifier = await GetUserModifierAsync(purpose, manager, user);

    return securityToken != null && TotpService.ValidateCode(securityToken, code, modifier, _userOption.TwoFactorTotpExpiration);
}

services.AddIdentity<ApplicationUser, ApplicationRole>()
    .AddEntityFrameworkStores<IdentityContext>()
    .AddDefaultTokenProviders()
    .AddTokenProvider<CustomTotpSecurityStampBasedTokenProvider >("CustomTotp");

var verificationCode = await _userManager.GenerateTwoFactorTokenAsync(user, "CustomTotp");

var verify = await _userManager.VerifyTwoFactorTokenAsync(user, "CustomTotp", request.VerificationCode);

<PackageReference Include="TotpGenerator" Version="1.0.2" />

private static readonly TimeSpan _timeStep = TimeSpan.FromSeconds(1);

public static bool ValidateCode(
    string securityStampToken,
    int code,
    string modifier,
    int expirationInMinutes)
{
    if (securityStampToken == null)
    {
        throw new ArgumentNullException(nameof(securityStampToken));
    }

    byte[] securityTokenBytes = GetBytes(securityStampToken);

    using (var hashAlgorithm = new HMACSHA1(securityTokenBytes))
    {
        for (var i = -Math.Abs(expirationInMinutes * 60); i <= 1; i++)
        {
            var currentTimeStep = GetNextTimeStepNumber(i);

            var computedTotp = ComputeTotp(hashAlgorithm, (ulong)((long)currentTimeStep), modifier);
            if (computedTotp == code)
            {
                return true;
            }
        }
    }

    // No match
    return false;
}

private static ulong GetNextTimeStepNumber(int seconds)
{
#if NETSTANDARD2_0
    var delta = DateTime.UtcNow.AddSeconds(seconds) - _unixEpoch;
#else
    var delta = DateTimeOffset.UtcNow.AddSeconds(seconds) - DateTimeOffset.UnixEpoch;
#endif
    return (ulong)(delta.Ticks / _timeStep.Ticks);
}