computer networks please helps with question #6 (1-4) 6. Consider the difference

Question

computer networks

please helps with question #6 (1-4)

6. Consider the difference between symmetric-key (SKS) and public-key systems (PKS). 1 (5 pts) Which requires sender and receiver to share the same key? SKS PKS 2. (5 pts) Which has different encryption and decryption keys? SKS PKS 3. (5 pts) If you have N users in a symmetric-key system who want to communicate amongst cach other in every possible pair confidentially, how many keys are required? (5 pts) If you have the same N users in a public-key system, and again want to prevent others from decoding your message, how many keys are required? 4.

Explanation / Answer

answer:

1)Symmetric key(SKS) cryptography systems use the same key for both to encrypt the plaintext and to decrypt the ciphertext.

So SKS requires sender and receiver to share the same key.

2)Public key(PKS) cryptography systems use different keys to encrypt to plaintext and to decrypt the ciphertext.

So PKS has different keys for encryption and decryption.

3) For the symmetric key, you can approach this problem as a complete graph with order N.With the vertexes representing people and the edges representing the symmetric keys. Then each vertex would have degree (N-1) and applying the Handshaking lemma, then number of edges would be:N(N-1)/2

So they would require N(N-1)/2 symmetric keys to have a secure communication between all of them.

4)For N users in public-key system of secure communication keys required are :2N

As in public-key system,each one would have 2 keys, so a total of 2N keys they require.

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