Why is JWT popular?

Summary

In this video, Sahn, co-author of system design interview books, explains the power and risks of JSON Web Tokens (JWTs) in web security. JWTs are widely used for secure information transmission between parties, utilizing a three-part structure: header, payload, and signature. The video covers signing algorithms, claims, and best practices for secure implementation. It also highlights potential vulnerabilities, such as token hijacking and cryptographic weaknesses. While JWTs offer portability and scalability, they can pose risks if not used carefully. Key security tips and JWT use cases in authentication and authorization are discussed.

Takeaways

• 🔒 JSON Web Tokens (JWTs) securely transmit identity over the web, but a stolen JWT can give hackers full access.
• 🧑‍💻 JWTs consist of three parts: the header, payload, and signature, each base64 encoded and separated by a period.
• 📋 The payload stores claims, which are statements about a user or entity. Claims can be registered, public, or private.
• 🔐 JWTs are usually signed, not encrypted, meaning that while the data is encoded, it can still be read if intercepted.
• 🛡️ There are two main signing algorithms: symmetric (HMAC SHA256) and asymmetric (RSA), each with different security trade-offs.
• 🚫 JWT payloads should never contain sensitive information unless encrypted, as they are not encrypted by default.
• ⏳ JWTs are stateless and not ideal for managing user sessions, as revoking tokens can be difficult.
• ⚠️ Common JWT vulnerabilities include token hijacking and weak cryptographic algorithms, which can be exploited.
• ✔️ Best practices for JWTs include keeping payloads small, using short expiration times, and securing tokens properly.
• 📈 JWTs offer scalability for authentication and authorization, but they can be vulnerable if not implemented securely.

Q & A

What is a JSON Web Token (JWT)?

A JSON Web Token (JWT) is a secure method for transmitting information between parties as JSON objects. It is widely used in web security for its ability to securely authenticate and authorize users.

How is a JWT structured?

A JWT consists of three parts: the header, the payload, and the signature. Each part is base64 encoded and separated by a period.

What information is typically included in the JWT header?

The JWT header usually contains the token type (JWT) and the algorithm used for signing, such as HMAC SHA256 or RSA.

What is the purpose of the JWT payload?

The payload of a JWT contains claims, which are statements about an entity (usually the user) along with additional data. Claims can be registered, public, or private.

Why should sensitive information not be included in a JWT payload?

Since JWTs are usually only signed and not encrypted, the payload can be read if intercepted. Therefore, sensitive information should not be included unless the payload is encrypted.

What are the two main types of JWT signing algorithms?

JWTs can be signed using symmetric algorithms, like HMAC SHA256, which use a shared secret key for both signing and verification. Alternatively, they can use asymmetric algorithms, like RSA, which use a public/private key pair.

What are some of the key advantages of using JWTs?

JWTs are self-contained and portable, making them useful for secure information exchange without requiring server-side storage. They are commonly used for authentication and authorization in standards like OAuth2 and OpenID Connect.

What are some of the key risks and vulnerabilities associated with JWTs?

JWTs can be vulnerable to token hijacking, where attackers steal a JWT to impersonate a user. They can also be exposed to cryptographic weaknesses, especially if weak hashing algorithms are used.

What are some best practices for securely using JWTs?

Best practices include keeping JWT payloads compact, using short expiration times, storing tokens securely, invalidating leaked tokens, and using strong signature algorithms.

When should JWTs not be used?

JWTs should not be used when handling highly sensitive data unless encryption is applied. They are also not ideal for managing user sessions due to their stateless nature, making session revocation difficult.

Outlines

00:00

🔐 Understanding the Basics of JSON Web Tokens (JWTs)

This paragraph introduces JSON Web Tokens (JWTs) as a secure method for transmitting information across the web. The analogy of losing a passport illustrates the risk of a stolen JWT, which grants full access to the hacker. It explains that the video will cover both the benefits and the risks of using JWTs. JWTs are defined as a way to securely transmit data between parties, formatted as JSON objects. The structure of a JWT is broken down into three parts: the header, payload, and signature, all base64 encoded and separated by periods. The header usually includes the token type (JWT) and the algorithm used (HMAC SHA256 or RSA). The payload contains claims, which describe information about the user or entity. JWTs are mostly signed but not encrypted, so sensitive data should not be stored unless first encrypted. JWTs provide a scalable and portable way to handle authentication and authorization, but users must be aware of potential vulnerabilities.

05:00

📜 JWT Structure and Signing Algorithms Explained

This paragraph delves deeper into the structure and signing mechanisms of JWTs. The payload of the JWT contains claims, which are statements about the user or entity and can include registered, public, or private claims. It emphasizes that while the payload is encoded, it is not encrypted, meaning it can be read if intercepted. The section then explains how JWTs are signed to ensure data integrity, with two main types of signing algorithms: symmetric (HMAC SHA256) and asymmetric (RSA). Symmetric algorithms use a shared secret key, while asymmetric ones use a public/private key pair. The benefits and drawbacks of each algorithm are also discussed, highlighting the importance of choosing the right one based on the application needs.

⚠️ JWT Risks and Vulnerabilities

Here, the focus is on potential risks and common vulnerabilities associated with JWTs. Token hijacking is a key issue, where attackers steal a valid JWT to impersonate the user. JWTs can also be vulnerable to weak cryptographic algorithms, making them susceptible to brute force attacks. It emphasizes the importance of strong security practices, such as using secure signing algorithms and limiting token expiration times. Additionally, the paragraph points out that JWTs are not ideal for managing user sessions because they are stateless, making it challenging to revoke access after issuance.

💡 Best Practices for Securing JWTs

This paragraph provides practical advice for securing JWTs. It recommends minimizing the payload to only include necessary claims, using short expiration times for tokens, securely storing tokens, and ensuring any leaked tokens are invalidated. It also stresses the importance of using strong signing algorithms to protect against token forgery or tampering. Following these best practices can help mitigate the risks associated with using JWTs in web applications.

👍 Pros and Cons of JWTs

The pros and cons of using JWTs are weighed in this paragraph. On the positive side, JWTs are self-contained, portable, and do not require server-side storage, making them highly scalable. However, the drawbacks include vulnerability to theft if intercepted and performance issues if too much information is stored in the payload, making the token large. The section concludes by reinforcing that while JWTs offer a scalable solution for authentication and authorization, they must be implemented carefully to avoid potential security risks.

📩 Subscribe to the System Design Newsletter

This final paragraph encourages viewers to subscribe to the System Design newsletter from ByteByteGo, which covers trending topics in large-scale system design. It highlights that the newsletter is trusted by over 500,000 readers and directs viewers to subscribe via their blog.

Keywords

💡JSON Web Token (JWT)

JSON Web Token (JWT) is a standard for securely transmitting information between parties as a JSON object. In the video, it is highlighted as a robust and portable method for identity verification and secure data transmission. JWTs consist of three parts: the header, the payload, and the signature, making them a cornerstone in web security.

💡Payload

The payload is the part of the JWT that contains the claims or data being transmitted. In the video, it is emphasized that the payload holds information like user details, and while it is base64-encoded, it is not encrypted by default. Therefore, sensitive data should not be included unless encryption is applied.

💡Header

The header is the first part of a JWT, containing metadata about the token, such as the type (usually 'JWT') and the signing algorithm (like HMAC SHA256 or RSA). The video explains that this part is crucial for identifying how the token was generated and verified, forming an essential part of JWT's structure.

💡Signature

The signature is the final part of the JWT, ensuring that the token hasn't been tampered with. It is created by encoding the header and payload, then signing them with a secret key (for symmetric algorithms) or a private key (for asymmetric algorithms). The video compares it to a wax seal on a letter to show its role in maintaining integrity.

💡Symmetric Algorithm

A symmetric algorithm uses the same secret key for both signing and verifying a JWT. In the video, algorithms like HMAC SHA256 are mentioned as examples. While fast and straightforward, these algorithms require secure key sharing between parties, making them less suitable for some scenarios.

💡Asymmetric Algorithm

Asymmetric algorithms, such as RSA, use a pair of keys: a private key for signing and a public key for verification. The video highlights this method as more secure for authentication without sharing a private key but notes that it is slower than symmetric algorithms. This method ensures that even if the public key is known, the token’s authenticity can still be verified without compromising security.

💡Claims

Claims are statements within the JWT payload about an entity (usually the user) and additional data. The video explains three types: registered, public, and private. Registered claims include predefined elements like the issuer and expiration time, while public and private claims allow more flexibility for custom data exchange.

💡Token Hijacking

Token hijacking occurs when an attacker steals a valid JWT and uses it to impersonate the legitimate user. In the video, this vulnerability is discussed as a major risk, as JWTs, when intercepted, can grant full access to resources unless preventive measures like token expiration and secure storage are in place.

💡Token Expiration

Token expiration refers to the setting of a time limit after which a JWT becomes invalid. The video advises using short expiration times to minimize the risk of token hijacking and other attacks. If a token is compromised, it will be less useful if it expires quickly.

💡OAuth2

OAuth2 is an authorization framework that often uses JWTs for authentication and secure resource access. In the video, it is mentioned as a standard protocol in which JWTs play a key role in managing identity and permissions across different systems without requiring direct password sharing.

Highlights

JSON Web Tokens (JWTs) allow secure identity transmission across the web, but a stolen JWT can give hackers full access.

JWTs consist of three parts: the header, payload, and signature, all of which are base64 encoded and separated by periods.

The header typically contains the token type (JWT) and the algorithm used, such as HMAC SHA256 or RSA.

JWT payloads store claims, which can be registered, public, or private, with predefined claims like issuer, expiration time, and subject.

While JWTs can be encrypted using JSON Web Encryption (JWE), most are signed but not encrypted, meaning the data is visible if intercepted.

JWTs should not carry sensitive information unless encrypted, as the data is easily accessible in transit.

Symmetric algorithms like HMAC SHA256 use a shared secret key, while asymmetric algorithms like RSA use a public/private key pair for signing.

JWTs are often used in OAuth2 and OpenID Connect for authentication and authorization.

JWTs are not suitable for managing user sessions as they are stateless, and revoking JWT access is difficult.

Common vulnerabilities include token hijacking, where an attacker steals a valid JWT, and cryptographic weaknesses, particularly when weak hashing algorithms are used.

To mitigate risks, use short expiration times, store tokens securely, invalidate leaked tokens, and use strong signature algorithms.

JWTs are self-contained and portable, eliminating the need for server-side storage.

If a JWT is intercepted, it can provide full access to resources, as the payload is not encrypted by default.

Large JWT payloads can negatively impact performance, especially if too much data is included.

Overall, JWTs offer a scalable solution for authentication and authorization if implemented with caution and best practices.

Transcripts

JSON Web Tokens let your  identity travel the web securely.

But like losing your passport, a  stolen JWT gives hackers full access.

In this video, we'll unlock the immense potential  of JWTs, and the dangers lurking within.

I'm Sahn, co-author of best-selling  system design interview books. We explain  

complex system design concepts clearly  through animations. Let's get started.

JSON Web Tokens, commonly known as JWTs,

are a robust method for securely transmitting  information between parties as JSON objects.

They have become a cornerstone in the  world of web security for good reasons.

First, let's talk about JSON itself.  It's a lightweight data interchange  

format that's easy to read and write for humans  and simple for machines to parse and generate.

It's the backbone of JWTs because  it represents its payload,  

which is where you store the  data you want to transmit.

Now, JWTs have a structure  of three parts: the header,  

the payload, and the signature. Each section  is base64 encoded and separated by a period.

The header typically consists of the token type,  

which is JWT, and the algorithm  being used, like HMAC SHA256 or RSA.

The payload of a JWT is  where you store the claims.

Claims are statements about an  entity, which is typically the  

user with some additional data. There are  three types of claims: registered, public,  

and private. Registered claims are predefined,  like the issuer, expiration time, and subject.

While JWT payloads can be encrypted using JSON Web  

Encryption (JWE), most implementations  use signed but not encrypted tokens.

This means that while the data is encoded, it  is not encrypted and can be read if intercepted.

That’s why sensitive information should  

never travel in a JWT payload  unless it's encrypted first.

Let's talk about signing these tokens.

Signing is like sealing an envelope with a wax  stamp to ensure it hasn't been tampered with.

There are two main types of signing algorithms:

Symmetric algorithms, like HMAC SHA256,  

use a shared secret key for  both signing and verification.

Asymmetric algorithms, such as RSA,  use a public/private key pair where  

the private key signs the token  and the public key verifies it.

When choosing an algorithm, consider  your needs. Symmetric keys are quick  

and simple but the secret key must be  shared between parties ahead of time.

Asymmetric keys allow verification of the creator  without sharing private keys but are slower.

Signed JWTs provide authentication, authorization,  and secure information exchange. Upon login,  

the server creates a signed JWT with user  details and sends it back. The client uses  

this to access protected resources by  sending the token in the HTTP header.

JWTs are commonly used in standards  

like OAuth2 and OpenID Connect for  authentication and authorization.

However, it's crucial to know when  not to use JWTs. The payload is  

not encrypted by default so should  not contain highly sensitive data.

Also, JWTs aren't ideal for managing user sessions  

since they are stateless. Revoking  JWT access can be challenging.

Some common vulnerabilities to be  aware of include token hijacking,  

where an attacker steals a  valid JWT to impersonate a user.

JWTs also could be vulnerable to  cryptographic weaknesses if using  

weak hashing algorithms. Automated brute force  attacks may try to crack token signatures.

To mitigate risks when using JWTs, some best  practices to follow are: keeping JWT payloads  

compact with only the necessary user claims; using short token expiration times when possible; 

storing tokens securely and invalidating any  leaked tokens; and using strong signature  

algorithms .

The pros are clear: JWTs are  self-contained, portable,  

and don’t require server-side storage. On the  downside, JWTs can be vulnerable to theft,  

and if intercepted, can provide full  access to resources. The payload can  

also get quite large if too much information  is included, which can affect performance.

Overall, JWTs provide a scalable way to  handle authentication, authorization,  

and information exchange if implemented carefully.

If you like our videos, you might like  our System Design newsletter, as well.

It covers topics in trends  and large-scale system design.

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