I recently came across an interesting article about refresh tokens, and one comment caught my attention. It suggested that instead of using refresh tokens to prevent the generation of new access tokens, we should just validate the access token and check if it's been blacklisted when it expires. The idea is that we could issue a new access token using the expired but not blacklisted one, maintaining the same security level and database check frequency as with refresh tokens. However, I'm confused about why refresh tokens are necessary if this method works. Can someone explain the advantages of refresh tokens over this proposed approach?
5 Answers
Refresh tokens have a key advantage: they’re used once and immediately invalidated. This makes them much safer because if someone intercepts your access token, they can continue to use it as long as it's valid. But with refresh tokens, since they're stored on the authentication service side, they're not easily accessible to anyone who might exploit your app. It limits the risk if an attacker tries to use an old token, which could lead to unauthorized access if they get hold of it!
The suggestion really changes the nature of how we use JWTs and could introduce some performance issues. With their typical use case, JWTs are stateless and don’t require backend verification for every request, which is part of their efficiency. If you have to check the blacklist for each access token, you're adding another reliance on the auth service and potentially slowing things down—especially for high-frequency requests!
Totally agree! If you go this route, you'd lose some of the simplicity and speed benefits that make JWTs appealing in the first place.
Just to add, the choice of using refresh tokens often comes down to the specifics of the application and its architecture. While there might be cases where what the comment suggests works, it generally adds complexity that most applications aren't prepared to handle. Going with what’s tried and tested can save a lot of headaches!
It’s worth mentioning that there are other strategies, like using opaque tokens or httpOnly cookies, which can sidestep some of the concerns with JWTs and refresh tokens entirely. If immediate session expiration is a priority, these alternatives might be more straightforward!
There’s also the broader point that many authentication standards include refresh tokens for a reason. They're a safe default because they allow a system to have different levels of trust—using a refresh token grants a longer-lived session while still giving you the flexibility to invalidate access tokens immediately if needed. It’s about balancing control and performance.
Exactly! Plus, if your app does have a security flaw, like XSS, even the refresh token is only valid for a limited time. This limits the potential damage since the attacker can only do so much before they need a new token.