![]() But then of course does not follow the principle that says that restful APIs should be stateless and that's why solutions like JWT became popular and effective. Restful APIs should always be stateless, and the most widely used alternative to authentication with JWTs is to just store the user's log-in state on the server using sessions. So there is no need to store any session state on the server, which of course is perfect for restful APIs. Json Web Tokens are a stateless solution for authentication. JWT is a very modern, simple and secure approach which extends for Json Web Tokens. For similar reasons, JWT should always be exchanged over a secure layer like HTTPS. Not doing so will mean that a man-in-the-middle attack is possible-a proxy server or ISP reads the cookies and then replays them later on pretending to be you. If you aren't then it's advisable to encrypt sensitive cookies themselves. If you are using HTTPS then everything is good. Cookies often contain unencrypted payloads. It's not too different from how cookies themselves work. This keeps JWT small in size and avoids inadvertent information leakage because everyone knows not to keep sensitive data in JWT. Once the server receives the JWT token and validates it, it is free to lookup the user ID in its own database for additional information for that user (like permissions, postal address, etc). A simple implementation makes adoption easier but it also lets each layer do what it does best (let HTTPS handle encryption). Once you know you have a secure channel between the server and client you can securely exchange JWT or whatever else you want. If dealing with a client like the web browser for example, you can store the JWT tokens in a cookie that is secure (is not transmitted via HTTP, only via HTTPS) and httpOnly (can't be read by Javascript) and talks to the server over an encrypted channel (HTTPS). The simplest reason is because it assumes this is a solved problem for the most part. The logical question is what is the motivation for not concerning itself with encrypted contents? Later on it verifies the payload and matching signature. The server adds a signature based on the payload when issuing a token to the client. That is to say, it can always get the answer for "Have the contents of this token been manipulated"? This means user manipulation of the JWT token is futile because the server will know and disregard the token. The short answer is that JWT doesn't concern itself with encryption. This is jarring for a lot of people initially. You can go to jwt.io, paste your token and read the contents. If I suppose that the recipient knows the secret, he CAN calculate the signature of any message and check if it's correct. You can't because you don't know which secret I used. Let's suppose, I send another person the message. This means if she changes something, the signature won't match anymore, and Bob will simply not accept the JWT anymore. ![]() She doesn't know the secret and has no way of finding it out. If however, Mallory changes something in the content, she isn't able to calculate the matching signature (which would be Hash(newContent + secret)). When receiving the message, Bob can also calculate Hash(payload + secret) to check whether the signature matches. To prevent that, Alice calculates Hash(payload + secret) and appends this as signature. Mallory doesn't know that secret, but wants to interfere and change the JWT. Let's assume Alice wants to send a JWT to Bob. Just to be sure: do you know and understand digital signatures? I'll just briefly explain one variant (HMAC, which is symmetrical, but there are many others). ![]() Otherwise, the receiver will notice that the signature won't match anymore.Īnswer to your comment: I'm not sure if I understand your comment the right way. If a token is signed, but not encrypted, everyone can read its contents, but when you don't know the private key, you can't change it. ![]() JWTs can be either signed, encrypted or both. ![]()
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