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Kerberos
Kerberos is a widely-used network authentication protocol designed to provide strong authentication for client/server applications through secret-key cryptography. Port 88 supports the Kerberos authentication system for securely verifying the identities of users and services across insecure networks. Both TCP and UDP transport mechanisms are employed depending on the use case, ensuring flexibility and reliability in various environments..
Kerberos is a secure authentication protocol originally developed at MIT as part of Project Athena. It utilizes symmetric key cryptography and a trusted third-party Key Distribution Center (KDC) to authenticate users and services over insecure networks without transmitting passwords in plaintext. The KDC issues time-limited tickets to users, which can then be presented to access network services securely.
When a user initially logs in, their client requests a Ticket Granting Ticket (TGT) from the KDC's Authentication Service (AS). Upon successful authentication, the TGT is used to obtain service tickets from the Ticket Granting Service (TGS), which allows the user to access specific services without re-entering credentials repeatedly. This mechanism helps maintain both usability and security.
Port 88 serves as the default communication point for both the AS and TGS using TCP and UDP protocols. UDP is typically used for lightweight, quick communication such as ticket requests, whereas TCP is employed when larger messages or reliability are required, such as in cross-realm authentication or when packet sizes exceed UDP limits.