Kerberos An Authentication Service for Computer Networks

Kerberos An Authentication Service for Computer Networks -...

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USC/ISI Technical Report number ISI/RS-94-399 Copyright © 1994 Institute of Electrical and Electronics Engineers. Reprinted, with permission, from IEEE Communications Magazine, Volume 32, Number 9, pages 33-38, September 1994. Click here to see Kerberos home page. Kerberos: An Authentication Service for Computer Networks B. Clifford Neuman and Theodore Ts'o When using authentication based on cryptography, an attacker listening to the network gains no information that would enable it to falsely claim another's identity. Kerberos is the most commonly used example of this type of authentication technology. Modern computer systems provide service to multiple users and require the ability to accurately identify the user making a request. In traditional systems, the user's identity is verified by checking a password typed during login; the system records the identity and uses it to determine what operations may be performed. The process of verifying the user's identity is called authentication. Password based authentication is not suitable for use on computer networks. Passwords sent across the network can be intercepted and subsequently used by eavesdroppers to impersonate the user. While this vulnerability has been long known, it was recently demonstrated on a major scale with the discovery of planted password collecting programs at critical points on the Internet [4] . Authentication, Integrity, Confidentiality, and Authorization Authentication is the verification of the identity of a party who generated some data, and of the integrity of the data. A principal is the party whose identity is verified. The verifier is the party who demands assurance of the principal's identity. Data integrity is the assurance that the data received is the same as generated. Authentication mechanisms differ in the assurances they provide: some indicate that data was generated by the principal at some point in the past, a few indicate that the principal was present when the data was sent, and others indicate that the data received was freshly generated by the principal. Mechanisms also differ in the number of verifiers: some support a single verifier per message, while others support multiple verifiers. A third difference is whether the mechanism supports non-repudiation, the ability of the verifier to prove to a third party that the message originated with the principal. Because these differences affect performance, it is important to understand the requirements of an application when choosing a method. For example, authentication for electronic mail may require support for multiple recipients and non-repudiation, but can tolerate greater latency. In contrast, poor performance would cause problems for authentication to a server responding to frequent queries. Other security services include confidentiality and authorization. Confidentiality is the protection of
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Kerberos An Authentication Service for Computer Networks -...

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