In
cryptography
Cryptography, or cryptology (from "hidden, secret"; and ''graphein'', "to write", or ''-logy, -logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of Adversary (cryptography), ...
, a key distribution center (KDC) is part of a
cryptosystem intended to reduce the risks inherent in exchanging
keys. KDCs often operate in systems within which some users may have permission to use certain services at some times and not at others.
Security overview
For instance, an administrator may have established a policy that only certain users may back up to tape. Many
operating system
An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ...
s can control access to the tape facility via a "system
service". If that system service further restricts the tape drive to operate only on behalf of users who can submit a service-granting ticket when they wish to use it, there remains only the task of distributing such tickets to the appropriately permitted users. If the ticket consists of (or includes) a key, one can then term the mechanism which distributes it a KDC. Usually, in such situations, the KDC itself also operates as a system service.
Operation
A typical operation with a KDC involves a request from a user to use some service. The KDC will use cryptographic techniques, mostly using
symmetric encryption, to authenticate requesting users as themselves. It will also check whether an individual user has the right to access the service requested. If the authenticated user meets all prescribed conditions, the KDC can issue a ticket permitting access.
In most (but not all) cases the KDC shares a
key with each of all the other parties.
The KDC produces a
ticket based on a
server key.
The
client receives the ticket and submits it to the appropriate
server.
The server can verify the submitted ticket and grant access to user submitting it.
Examples
Security systems using KDCs include
Kerberos. (Actually, Kerberos partitions KDC functionality between two different agents: the AS (Authentication Server) and the TGS (Ticket Granting Service).)
References
External links
Kerberos Authentication Protocol{{Webarchive, url=https://web.archive.org/web/20120317034215/http://www.zeroshell.net/eng/kerberos/Kerberos-operation/ , date=2012-03-17
* Microsoft
Kerberos Key Distribution Center - TechNet* Microsoft
Key Distribution Center - MSDN
Key management
Computer network security