다중 요소 인증(MFA)

Welcome! Today, we're diving into Multi-Factor Authentication (MFA), an essential security layer for any modern SaaS application.

MFA adds extra steps to verify a user's identity beyond just a password. It significantly boosts security by making it harder for unauthorized users to access accounts, even if they know your password.

Passwords alone are often not enough. They can be:

• Stolen through phishing
• Guessed through brute force attacks
• Exposed in data breaches

MFA protects user accounts by requiring more than one type of verification, drastically reducing the risk of account takeover.

MFA relies on at least two of these three categories:

• Something you know: A password, PIN, or security question.
• Something you have: A phone, hardware token, or authenticator app.
• Something you are: Biometrics like a fingerprint, face scan, or voice.

Combining factors makes authentication much stronger.

One of the most common MFA methods is the One-Time Passcode (OTP). These are temporary, typically 4-8 digit codes sent to a user's registered device or email.

OTPs are valid for a very short period (e.g., 60-300 seconds) and can only be used once.

On the server, generating an OTP is often a matter of creating a random number. Here's a basic Java example:

Once an OTP is generated:

• It's stored temporarily on the server, usually associated with the user's session and an expiration time.
• It's sent to the user (e.g., via SMS or email).
• When the user enters the OTP, the server compares it to the stored code.
• If they match and the code hasn't expired, authentication is successful.

Remember to delete the OTP after successful verification or expiration.

Time-based One-Time Passwords (TOTP) are generated by apps like Google Authenticator or Authy. These codes change every 30-60 seconds.

TOTP doesn't rely on network connectivity (like SMS), making it more reliable and often more secure.

TOTP works using a shared secret key. This is a unique, random key generated by the server when a user enrolls in MFA.

• The server stores this secret.
• The user scans a QR code containing this secret into their authenticator app.

Both the server and the app then use this same secret, along with the current time, to generate identical OTPs.

The authenticator app and server independently calculate the TOTP using:

• The shared secret key.
• The current time (divided into time steps, e.g., 30 seconds).
• A cryptographic hash function (e.g., HMAC-SHA1).

This ensures that both parties arrive at the same 6-digit code within the same time window, without needing to communicate over the network for each login.

Which of the following best describes the 'something you have' factor in Multi-Factor Authentication?

Great job! You've learned the fundamentals of Multi-Factor Authentication.

• MFA adds crucial security by requiring multiple verification factors.
• It uses 'something you know', 'something you have', or 'something you are'.
• Common methods include SMS/Email OTPs and Authenticator Apps (TOTP).
• Implementing MFA involves generating, storing, and verifying these temporary codes or shared secrets.

Next, we'll explore how to manage user permissions with Role-Based Access Control (RBAC).