Handout 6 - Key Distribution Examples

Handout 6 - Key Distribution Examples -...

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CIS 3360 Security in Computing Spring 2010 Handout # 5 – Key Distribution Examples Legend: E() means encryption  function K s  is session key KR a  is private key of A KU a  is public key of A Example 1: The following two messages are exchanged between B and A. Assume that f is a  function and notations used here are the same used in class lecture.  Will both A and B be able to decrypt the messages sent by other? Justify your answer.  What is accomplished through these communications? B   A:   E(K S , N 2 ) A   B:  E(K S , f(N 2 )) Answer:  Yes. From these two messages we see that both A and B used Ks to encrypt the  message.  Since both of them share the same key Ks, they will be able to decrypt the received  message. Since N2 is a nonce, B is sending a challenge to A. A is responding by computing   f(N 2 ) to B.  This is a challenge response strategy. Example 2: Consider A, B and C. Assume each node knows its own private and public keys.  A 
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This note was uploaded on 10/05/2010 for the course CIS CIS 3360 taught by Professor Guha during the Spring '10 term at University of Central Florida.

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Handout 6 - Key Distribution Examples -...

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