How Long Does a JWT Secret Key Last Before It Needs to Be Changed?

For those who don't know, technically, in short, a JWT secret key can last forever, which means it doesn't have any expiry date. The practical answer is that the JWT secret key has to be changed regularly due to various security reasons. As per your attack risk, you should always change your JWT secret key every six to twelve months. Whenever you feel there is some breach happening or the chance of the key getting leaked for any reason, then you should immediately change your JWT secret key.

Changing your key at a certain interval of time is the best way to prevent long-term damage from silent leaks. It makes your entire system more attack-proof. Also, striking the right balance between robust security and seamless system updates is key to a secure application.

What Is a JWT Secret Key?

A JWT Secret Key is a private key that is used in an application to sign and verify tokens. Think of this as a hidden password that the server uses to sign tokens, verifying that they are authentic and safe. It is stored in the backend, and if any user wants to see the JWT secret key, they can't see it because it is never exposed to the world. Its function is stored in the server and does its job.

Does the Secret Key Have an Expiry Date?

The short and simple answer to this question is NO. The secret key does not have a fixed expiry date. It remains valid forever until you change it yourself on your application. There is nothing like automatic expiration and updation of the secret key. You have to manually change it. It will continue to work as long as the key is on your server.

Why is it Necessary to Replace It?

It is necessary to replace it because of various security reasons, such as if your secret key gets leaked or misused, then all your data can be compromised. The number of attacks can increase over time. Following current date safety and security practices can represent a trusted application or website, as it increases the overall value. Here are some more reasons to rotate your secret key:

• To update an old system—a system where the same 'key' might have been in use for years.
• In case you accidentally or unknowingly expose your key.
• To maintain robust security over time.

How Often Should You Change Your Secret Key?

There is no single fixed rule to change your secret key. It mostly depends on your application. If your application is built for normal usage, then you should consider changing your secret key every 3 to 6 months. If your application is built for heavy and complex usage, and at the same time, the risk of being attacked is high, then you should change your key every 1 to 3 months. However, if you ever feel that you may get hacked or your key gets leaked, then you should immediately update your key.

Because if you didn't change your key over a long time. During that time, if someone got hold of the key, then they could easily get access to your system, and you have no option to stop them without updating your key with a new one.

That's why changing the key every couple of months can make your risk window much smaller.

What is Key Rotation?

The process of changing your secret key periodically is called Key Rotation. It is considered good security practice in the developer world, as recommended by OWASP's JWT security guidelines.

How to Perform Key Rotation

One thing you should keep in mind during key rotation is that you should do it gradually so that you don't log out all your users at once. Here are the steps:

Step 1: First, generate a new key. You can use a cryptographically secure method "likecrypto.randomBytes(64)".

Step 2: For existing users, not being suddenly kicked out. You should allow both the old and new keys for a while so that all users get time to refresh their tokens.

Step 3: Once you feel that most users have received the new tokens, then you gradually remove the old key.

JWT Expiry vs Secret Key

There is confusion among many developers about these two. I must tell you that they are completely different things. JWT expiration is a security feature that determines how long a token can be used. The "exp" (expiration time) claim specifies when the token becomes invalid and when the server should no longer accept it. On the other side, the JWT secret key is used to sign and verify the token. Although the JWT payload is encoded (and not encrypted), it remains visible to anyone who possesses the token.

Things You Should Know

• The secret key should always be strong and long.
• You should never put this in your source code in any place.
• Always store in a .env file or in a secure vault.
• You should gradually do key rotation so that it doesn't affect your existing users.

Best Practices

• You sould keep your individual tokens lived short.
• Regular key rotation.
• If compromised then replace your keys immediately.
• You should track unsual activity so that you can notice any leak.