6-3-4 Kerberos Explained

Key Concepts

• Kerberos Protocol
• Key Distribution Center (KDC)
• Ticket Granting Ticket (TGT)
• Service Ticket
• Authentication and Authorization

Kerberos Protocol

Kerberos is a network authentication protocol that uses tickets to allow nodes to prove their identity over potentially insecure networks. It is designed to provide strong authentication for client/server applications by using secret-key cryptography.

Key Distribution Center (KDC)

The KDC is a trusted third-party server that issues tickets to users and services. It consists of two main parts: the Authentication Server (AS) and the Ticket Granting Server (TGS). The AS verifies the user's identity and issues a TGT, while the TGS issues service tickets based on the TGT.

Ticket Granting Ticket (TGT)

A TGT is a ticket issued by the AS to a user upon successful authentication. The TGT is encrypted with the KDC's secret key and can only be decrypted by the KDC. It is used by the user to request service tickets from the TGS without needing to re-authenticate.

Service Ticket

A service ticket is issued by the TGS to a user, allowing them to access a specific service. The service ticket is encrypted with the service's secret key and can only be decrypted by the service. It contains the user's identity and permissions, ensuring secure access to the service.

Authentication and Authorization

Kerberos provides both authentication and authorization. Authentication is the process of verifying the identity of a user, while authorization is the process of granting access to specific resources based on the user's identity and permissions. Kerberos ensures that only authenticated users with the appropriate permissions can access services.

Examples and Analogies

Think of Kerberos as a secure building with multiple rooms. The KDC is like the building's security office, which issues keys (tickets) to visitors (users). The TGT is like a master key that allows visitors to request additional keys (service tickets) for specific rooms (services) without needing to go back to the security office.

Service tickets are like room keys that grant access to specific rooms. Each room key is encrypted with the room's lock code, ensuring that only authorized visitors can enter. This system ensures that visitors are properly authenticated and authorized to access the rooms they need.