11. Assume you are responsible for security of a company. The public key of your company...

 

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11. Assume you are responsible for security of a company. The public key of your company is available to many organizations. The company wants to send a secret message m to another company using asymmetric encryption. The problem is, if your company encrypts messages intended to another company with its private key, other companies can also decrypt those with the public key of your company. Both companies also share a secret key, S. The symmetric and asymmetric key values along with the associated two prime numbers of these companies are given: Your task: Your company wants to send message m to another company using some of the above keys and values. Both companies have agreed to achieve the following security objectives: 1) Your company wants that the other company cannot deny that it had received the message m. Similarly, the other company wants to make sure that your company cannot deny that it had sent the message to the other company. 2) No one, except these two companies, can retrieve the message m. Your task: 3 a) How do these two companies achieve the above security objectives with the above available keys and values. Show all calculations and intermediate values of the encryptions and decryptions. Explain briefly each step of the action/calculation done by the parties and the associated values. b) Explain briefly how the security objective (1) is achieved by which step of your calculations shown in question (a). 11. Assume you are responsible for security of a company. The public key of your company is available to many organizations. The company wants to send a secret message m to another company using asymmetric encryption. The problem is, if your company encrypts messages intended to another company with its private key, other companies can also decrypt those with the public key of your company. Both companies also share a secret key, S. The symmetric and asymmetric key values along with the associated two prime numbers of these companies are given: Your task: Your company wants to send message m to another company using some of the above keys and values. Both companies have agreed to achieve the following security objectives: 1) Your company wants that the other company cannot deny that it had received the message m. Similarly, the other company wants to make sure that your company cannot deny that it had sent the message to the other company. 2) No one, except these two companies, can retrieve the message m. Your task: 3 a) How do these two companies achieve the above security objectives with the above available keys and values. Show all calculations and intermediate values of the encryptions and decryptions. Explain briefly each step of the action/calculation done by the parties and the associated values. b) Explain briefly how the security objective (1) is achieved by which step of your calculations shown in question (a).