OTP Mechanism in Asp.Net core

OTP mechanism can be done using different algorithms like TOTP or HOTP. To use it we have inbuilt plugins available,

I have used Otp.Net and TOTP algorithm for this purpose, we can refer it from https://github.com/kspearrin/Otp.NET

Step 1: Refer library from Nuget "Otp.Net" https://www.nuget.org/packages/Otp.NET

Step 2: Create TOTP Object

var emailToSend ="balajisrmv@gmail.com";

var secretKey = Encoding.ASCII.GetBytes(emailToSend);

var TotpObj = new Totp(secretKey, step: 60); //set step for 60 secs for OTP expiration

var otpString = TotpObj.ComputeTotp();

//Send to email, you can customize this to however needed.

emailService.SendEmail(toAddress: emailToSend, subject: "OTP Subject", body: "Your otp code is: " + otpString);

Step 3: Send this otpString to any channel like Email or SMS as your covenient

Step 4: Create seperate action method to validate input OTP code from user

public IActionResult OnPostVerifyAuthCodeAsync(string OtpCode)

        {

   var emailToSend ="balajisrmv@gmail.com";

   var secretKey = Encoding.ASCII.GetBytes(emailToSend);

   var TotpObj = new Totp(secretKey, step: 60); //set step for 60 secs for OTP expiration            

bool otpValid = TotpObj.VerifyTotp(OtpCode, out long timeStepMatched, new VerificationWindow(2, 2));

            if (otpValid)

            {

               

//OTP is valid proceed your business logic            

            }

            else

            {

               //OTP is invalid throw error

     }

            return Page();

        }