Let’s look at the topics included in this blog on ‘What is Kerberos?’:
What is Kerberos?
It is a network authentication protocol that uses third-party authorization for validating the profiles of users. It also employs symmetric key cryptography for plaintext encryption and ciphertext decryption. The keys in cryptography consist of a secret key that shares confidential information between two or more objects.
In short, it helps in maintaining the privacy of an organization. Now, since you understood what Kerberos is, you might be thinking why Kerberos. There are various authorization protocols, but it is an improved version among all of them. It really becomes difficult for cybercriminals to break into the Kerberos authentication system. There will be flaws in an organization that need to be managed by using Kerberos for defending itself from cybercriminals. The tool is used by popular operating systems such as Windows, UNIX, Linux, etc. With the use of authentication system, the Internet has become a more secure place.
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Parameters of Kerberos
There are three main parameters used in Kerberos, and they are:
- Key Distribution Center (KDC)
These three components act as a third-party authentication service.
Also, it uses cryptography for maintaining mutual privacy by preventing the loss of packets while transferring over the network.
Further, in this blog, we will try to understand how Kerberos works.
What is Kerberos Used for?
Nowadays, Kerberos is used in every industry for maintaining a secure system to prevent cybercrimes. The authentication protocols of it depend on regular auditing and various authentication features. The two major goals of Kerberos are security and authentication.
It is used in e-mail delivery systems, text messages, NFS, signaling, POSIX authentication, and many more. It is also used in various networking protocols, such as SMTP, POP, HTTP, etc. Further, it is used in client/server applications and in the components of different operating systems to make them secure.
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How does Kerberos work?
We have already discussed in the previous sections about Kerberos being an authentication protocol. It is proved to be one of the essential components of client/server applications and used in various fields for network security, providing mutual authentication. In this section, we will discuss how Kerberos works. For that, first, we need to know the components of it.
Components of Kerberos
It mainly provides two services, and they are:
- Authentication service
- Ticket granting service
For providing these services, it uses its various components. Further, let’s discuss these principal components used for authentication:
1. Client: The client helps initiate a service request for communicating with the user.
2. Server: All the services required by the user are hosted by the server.
3. Authentication server (AS): As the name suggests, it is used for the authentication of the client and the server. It assigns a ticket through TGT (ticket granting ticket) to the client. The assigned ticket ensures the authentication of the client to other servers.
4. Key distribution center (KDC): There are three parts to the Kerberos authentication service:
- Ticket granting service (TGS)
- Authentication server (AS)
These parts reside in a single unit known as the key distribution center.
5. Ticket granting server (TGS): This server provides a service to assign tickets to the user as a unique key for authentication.
There are unique keys used by the authentication server and the TGS for both the clients and the servers. Now, let’s look at the cryptographic secret keys used for authentication:
- Client/User secret key: It is the hash of the password set by the user that acts as the client/user secret key.
- TGS secret key: It is the secret key that helps in deciding TGS.
- Server secret key: The server secret key helps determine the server that is providing the services.
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Architecture of Kerberos
Now, we will understand how Kerberos works by checking out its architecture. The below diagram shows the workflow of the Kerberos protocol:
Here are the steps involved in the Kerberos workflow:
Step 1: Initially, there is an authentication request from the client. The user requests TGS from the authentication server.
Step 2: After the client’s request, the client data is validated by KDC. The authentication server verifies the client and the TGS from the database. It then generates a cryptographic key (SK1) after checking both the values, implementing the hash of the password. The authentication server also computes a session key. This session key uses the secret key (SK2) of the client for the encryption.
Step 3: Then, the authentication server creates a ticket that consists of the ID, network address, secret key, and the lifetime of the client.
Step 4: The decryption of the message is then performed by the client using the client’s secret key.
Step 5: Now, the client demands entrance into the server using TGS. The ticket generating service creates a ticket that acts as an authenticator here.
Step 6: Another ticket is generated by KDC for the file server. Then, the TGS decrypts the ticket for obtaining the secret key initiated by the client. It checks the network address and the ID by decrypting the authenticator. If the client ID and the network address match successfully, then KDC shares a service key with the client and the server.
Step 7: The client utilizes the file ticket for authentication. The message is decrypted using SK1 to obtain SK2. Again, the TGS generates a new ticket to send to the target server.
Step 8: Here, the target server decrypts the file ticket by using the secret key. After that, the server performs checks on the client details by decrypting SK2. The target server also checks the validity of the ticket. Finally, when all the client’s encrypted data is decrypted, and the data is verified, the server authenticates the client to use the services.
This is how we use and implement the Kerberos protocol for securing a system and the client-server interactions.
Advantages of Using Kerberos Authentication
1. Enhanced security: Authorization from third parties, multiple secret keys, and cryptography make it one of the most reliable authentication protocols in the industry. When using it, passwords for the users are never sent through the network. In an encrypted form, the hidden keys move through the device. Also, it becomes impossible to collect enough data to impersonate a customer or a service, even if someone is recording conversations.
2. Access control: It is a key part of the businesses of the day. The protocol enables the best access control. With the help of this protocol, a business gets a single point for upholding safety protocols and keeping records of logins.
3. Transparency and auditability: For auditing processes and inquiries, transparent and accurate logs are important. It makes clear to see who was calling for what at what moment for maintaining transparency.
4. Shared authentication: It allows users and service systems to authenticate each other. Both the users and the server systems can understand that they are communicating with valid partners at each stage of the authentication process.
5. Limited-lifetime ticket: All tickets have serial numbers and lifelong data in the Kerberos model. Admins can monitor the authorization time of the users. For avoiding brute-force and repeat attacks, short ticket lifetimes prove to be beneficial.
6. Scalability: Several tech companies, including Apple, Microsoft, and Sun, have implemented this authentication system. The acceptance among companies speaks volumes about the capability of Kerberos to keep up with the needs of large firms.
7. Reusable authentications: The authentication of Kerberos is reusable and robust. The users need to verify devices with Kerberos only once. They can verify network services for the lifespan of the ticket without having to re-enter personal information.
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Is Kerberos outdated?
Despite the potential of hackers to bypass it, Kerberos is far from extinct and has proved to be an enhanced security-access control protocol. It’s key advantage is its ability to use powerful symmetric encryption to secure credentials and tickets for authorization.
Presently, it would take a very long time to hack a system that is backed by any AES encryption method with the latest version of Kerberos. Therefore, it will be around in some form or the other in the arena of system security as there are no legitimate rivals to replace Kerberos as of now.
Scope of Using Kerberos
In this blog, we discussed what Kerberos is and the authentication workflow of Kerberos in a simple way. However, practically, the implementation of the Kerberos authentication process is much more complex. Kerberos allows companies to use its centralized authentication server for using protocols that help build security walls for software applications.
It serves as the base authentication protocol used in the industry for making secure software apps. It has been a proven security solution for a long period. Most of the operating systems use it for creating encryption algorithms. The importance of Kerberos is not going to step down until we get another method that is better than Kerberos.
This ‘What is Kerberos?’ blog ends here, and it has explained all about how Kerberos serves as the base for securing applications.
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