Can I code this? A Two-Factor Authentication Service
Generating a time-based one-time code is a well-documented, simple algorithm. Being the trusted identity layer other applications rely on to keep their users' accounts secure is a different, much higher-stakes undertaking.
Just pay
Effort: not worth startingRunning cost: $0/mo to start
Why CanICodeThis says Just pay
Generating a TOTP (time-based one-time password) code from a shared secret follows a well-documented, open standard (RFC 6238)
For your own single app's login flow, adding TOTP-based 2FA using an established library is genuinely a reasonable weekend addition
Displaying a QR code for a user to scan into their own authenticator app is a solved, simple pattern
The parts that'll cause problems
Becoming a general-purpose 2FA PROVIDER that other applications integrate with and trust is a security-critical role — if your service has a flaw, every app that relies on it inherits the risk
Secure secret storage and recovery-code handling for account lockouts have a long history of subtle implementation mistakes even experienced teams make
This is a case where 'adding 2FA to my own app' (genuinely doable) and 'building a 2FA service for others to rely on' (genuinely not) are very different projects wearing the same name
How I'd build this
frontend
Next.js
hosting
Vercel
MVP scope
If the real goal is securing your own app: add TOTP 2FA to your existing login using an established library, not from scratch
Postpone to v2
Becoming a 2FA provider for other applications (genuinely high-stakes security infrastructure — use an established provider like Okta or Twilio instead)
What it actually costs to build
AI agent — with a subscription (Claude Pro/Max, Cursor, etc.)
$0 marginal
AI agent — pay-per-use API, no subscription
$86–$172 one-time
Hosting, once it's running
$0/mo (free tier)
Domain name, if you want your own
~$12/yr
Existing tools solving a similar problem typically run $2.99–$2.99/mo — see how they compare below.
The build prompt
Add TOTP two-factor authentication to your own app's login — genuinely achievable with an established library:
1. Use a well-audited TOTP library (implementing RFC 6238 yourself is exactly the kind of place small mistakes become real vulnerabilities).
2. Generate and display a QR code for the user to scan into their authenticator app.
3. Verify the 6-digit code on login using the same library.
That part is a genuinely reasonable, achievable addition to an existing login flow. Out of scope, and a different category of problem: becoming a 2FA PROVIDER other applications integrate with and trust — genuinely high-stakes security infrastructure. Use an established provider like Okta or Twilio if that's actually what you need.