If this feels jargon-laden and confusing right out of the gate, don't worry! Let's break it down into smaller, distinct steps. In this case, the private key is used by the token issuer (authorization server), and the public key is used by the application receiving the token in order to validate it. RSA256 is an Asymmetric Key Cryptography algorithm, which uses a pair of keys: a public key and a private key to encrypt and decrypt. RS256 is an RSA Digital Signature Algorithm with SHA-256. Let's go through it step-by-step.įor this article, I'm going to assume use of an RS256 signing algorithm. This is where the missing steps of the owl JWT signing / validation process are. (If an asymmetric signing algorithm was used, different keys are used to sign and validate if this is case, only the authorization server holds the ability to sign tokens.) When the client receives the ID token, the client validates the signature using a key as well. When an authorization server issues a token, it signs it using a key. JWTs are signed so they can't be modified in transit. The final segment is the crypto segment, or signature. It is base64Url encoded (byte data represented as text that is URL and filename safe).Įnter fullscreen mode Exit fullscreen mode The header segment is a JSON object containing a signing algorithm and token type. JSON Web Tokens are composed of three URL-safe string segments concatenated with periods. We covered the anatomy of JWT in depth in the previous blog article on authentication and authorization, but let's do a very brief recap. While you generally should not sign and validate tokens yourself (seriously, leave this to the experts - identity providers and Identity-as-a-Service platforms!), knowing how it works can be helpful in making you feel more comfortable with using JWTs. Okay, but you're reading this because you still want to know the missing steps to draw the owl. This is why you don't need to know the exact process for signing and validating JWT in order to effectively use them for authenticating and authorizing your applications and APIs. We trust that the manufacturers have used their expertise, specifications and standards, and due diligence to make useful tools for us to be more effective at the jobs we need those tools for. We can still be good drivers or great computer programmers without intimate knowledge of these things. □ When you charge your laptop, do you need to know what chemical reactions take place in a lithium ion battery to create the flow of electrons in a circuit to store and produce energy? Nope! □ When you get into your car to drive to the grocery store, do you need to know how internal combustion works? You don't. Think of it this way: for human beings to be effective or skilled with a tool, we don't need to know the intricacies of the tool's components. Why is this? Why do most JWT resources simply say "and then you sign and validate" and leave it at that? Why Don't We Need to Know How Signing and Validation Work? Instead of learning simpler, incremental steps to aid in my understanding, it felt like I was being given ten more complex, complete owl drawings. Most of the resources I dug up took me deep down the rabbit hole - until my head was swimming with mind-melting jargon, Alices and Bobs (placeholder names used in cryptography examples), and complex maths. To me, not being able to find approachable information about signing and validating JWT felt like the missing steps to draw the owl. The meme demonstrates "How to draw an owl": There's a meme about being introduced to a concept and then there are steps missing while you're expected to be able to get to the end result without knowing the steps in between. JWTs are signed with a key when they are generated and then validated with a key upon receipt so we can verify that they haven't been modified in transit.The JWT format is defined by IETF specification RFC 7519 and is composed of three segments ( a header, a payload, and a crypto segment.JSON Web Tokens (or JWT) are a compact, URL-safe way to transfer pieces of data between two parties (such as an authorization server and an application).Information about them is readily available from many sources, chiefly covering: JWTs are - in general terms - reasonably approachable. I recommend that you read that post first. Note: This article is a companion to my post on Authorization and Authentication for Everyone. This article aims to demystify signing and validating JSON Web Tokens, with little need for security or cryptography knowledge. When I started learning about JSON Web Tokens, there were some things that were straightforward to understand - and some concepts that felt like "hidden secrets" of JWT lore.
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