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Authors:
James F. Kurose, Keith W. Ross
Chapter:
Security In Computer Networks
Exercise:
Review
Question:6 | ISBN:9780132856201 | Edition: 6

Question

Suppose N people want to communicate with each of N – 1 other people using symmetric key encryption. All communication between any two people, i and j, is visible to all other people in this group of N, and no other person in this group should be able to decode their communication. How many keys are required in the system as a whole? Now suppose that public key encryption is used. How many keys are required in this case?

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Answer

Let us take N people want to communicate with each of N – 1 other people using symmetric key encryption.

All communication to all other people in this group of N, and no other person in this group should be able to decode their communication.

Then the required in the system as a whole is N*(N-1)/2.

Let us take that public key encryption is used.

Then the required in this case  as a whole is N*(N-1)/2N.

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