Question: Two users wish to establish a secure communication channel and exchange a session key after mutual authentication. Show how this can be done with the hclp of a $\mathrm{KDC}$ .
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mumbai university • 319 views
 modified 4 months ago  • written 4 months ago by
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• Key Distribution Center (KDC) is a central authority dealing with keys for individual computer ( nodes) in a computer network.

• It is similar to the concept of the authentication Services (AS) & Tichel Granting Service (TGS) in Kerheros.
• The basic idea is that every node shares an unique secret key with the KDC. Whenever user wants to communicate securely with user B , the following action take place.
• The background is that A has a secured secret key KA with KDC . Similarly B is assumed to share a secret key KB with the KDC.

• A sends a request to KDC encrypted with KA , which includes:

• Identifies of A & B

• A random number R , called as names.

• KDC responds with a message encrypted with KA , continuing :

a. One - time symmetric key KS.

b. Original request that was sent by A, for verification

c. Plus, KS encrypted with KB & ID of A encrypted with KB.

• A & B can now communicate by using KS for encryption