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What is Kerberos Authentication?
It is a network authentication protocol that uses third-party authorization for validating user profiles. It also employs symmetric key cryptography for plain-text encryption and cipher-text 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 have understood what Kerberos is, you might be thinking why Kerberos. There are various authorization protocols but Kerberos is an improved version among all. 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 the Kerberos authentication system, the internet has become a more secure place.
Parameters of Kerberos
There are three main parameters that are used in Kerberos. They are:
- Key Distribution Center (KDC)
These three components act as a third-party authentication service.
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.
Kerberos is used in email delivery systems, text messages, NFS, signaling, POSIX authentication, and much more. It is also used in various networking protocols, such as SMTP, POP, HTTP, etc. Further, it is used in client or server applications and in the components of different operating systems to make them secure.
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We have already discussed in the previous sections about Kerberos being an authentication protocol. It has proved to be one of the essential components of client or server applications. It is also used in various fields for network security and providing mutual authentication. In this section, we will discuss how Kerberos works. For that, first, we need to know about Kerberos’s components.
Components of Kerberos
Kerberos mainly provides two services. They are:
- Authentication service
- Ticket-granting service
For providing these services, Kerberos uses its various components. Further, let us discuss the following principal components that are used for authentication:
The client helps to initiate a service request for communicating with the user.
All the services that are required by the user are hosted by the server.
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3. Authentication Server (AS)
As the name suggests, AS is used for the authentication of the client and the server. AS assigns a ticket through Ticket Granting Ticket (TGT) 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 Server (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 that are used by the authentication server and the TGS for both clients and servers. Now, let us look at the cryptographic secret keys that are used for authentication:
- Client or User Secret Key: It is the hash of the password set by the user that acts as the client or user secret key.
- TGS Secret Key: It is the secret key that helps in deciding TGS.
- Server Secret Key: It helps to determine the server that provides the services.
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Architecture of Kerberos
Now, we will understand how Kerberos works by checking out its architecture. The following diagram shows the workflow of the Kerberos protocol:
The following steps are 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 the KDC. The authentication server verifies the client and the TGS from the database. The authentication server then generates a cryptographic key (SK1) after checking both values and implementing the hash of the password. The authentication server also computes a session key. This session key uses the secret key of the client (SK2) for encryption.
Step 3: The authentication server then creates a ticket that consists of the ID, network address, secret key, and lifetime of the client.
Step 4: The decryption of the message is then performed by the client by using the client’s secret key.
Step 5: Now, the client demands entrance into the server by using TGS. The TGS 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 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 by 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 of the client’s encrypted data is decrypted and 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 client-server interactions.
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Advantages of Kerberos Authentication
1. Enhanced security
Authorization from third parties, multiple secret keys, and cryptography make Kerberos one of the most reliable authentication protocols in the industry. When using Kerberos, passwords for the users are never sent through the network. They are sent in an encrypted form and the hidden keys move through the device. It becomes impossible to collect enough data to impersonate a customer or 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 login records.
3. Transparency and auditability
Transparent and accurate logs are important for auditing processes and inquiries. It clarifies who was calling for what and at what moment for maintaining transparency.
4. Shared authentication
It allows users and service systems to authenticate each other. Users and 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. Short ticket lifetimes prove to be beneficial for avoiding brute-force and repeat attacks.
Several tech companies, including Apple, Microsoft, and Sun, have implemented the Kerberos authentication system. This level of acceptance speaks volumes about the capability of Kerberos to keep up with the needs of large companies.
7. Reusable authentications
The authentication of Kerberos is reusable and robust. 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. Kerberos’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 have discussed what Kerberos is and its authentication workflow 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 to build security walls for software applications.
Kerberos serves as the base authentication protocol that is used in the industry for making secure software apps. It has been a proven security solution for a long period. Most operating systems use it for creating encryption algorithms.
This blog about Kerberos ends here; it has covered all about how Kerberos serves as the base for securing applications.
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