Network Security and Secret key question, Need help A small private club has onl

Question

Network Security and Secret key question, Need help

A small private club has only 100 members. Answer the following questions:

a. How many secret keys are needed if all members of the club need to send secret messages to each other?

b. How many secret keys are needed if everyone trusts the president of the club? If a message needs to send a message to another member, she first sends it to the president; the president then sends the message to the other member.

c. How many secret keys are needed if the president decides that the two members who need to communicate should contact him first? The president then creates a temporary key to be used between the two. The temporary key is encrypted and sent to both members.

Explanation / Answer

We can solve the problem by using asymmetric algorithm for encryption which uses one public key and one private key.

1. If so there are 100 members in a club then, 200 keys are required as 1 private key and 1 public key for each person( For example, consider two users of a cryptosystem: Alice and Bob. Each has a pair of public and private keys and distributes their public keys freely to other users. If Alice wants to send a message to Bob, she encrypts it with Bob's public key (which everyone knows). When he receives the message, he uses his own private key (known only to him) to decrypt it. This solves our scalability issue by requiring only two keys per user.)

2. 101.(100 Private keys for members and 1 private key for president).

3. 50(As two members will be communicating via a temporary key)

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