# VU CS315 Assignment no. 1 Fall 2022

• Question No.1

Consider a network scenario where two users (User-1 and User-2) want to devise a common secret key so that the exchange of important information among them can be made secure by the use of some symmetric encryption technique. In order to encounter the challenge of exchanging the common secret key among them in insecure channel but in secured manners, both the users have agreed upon the use of the Diffie-Hellman Algorithm and to perform the following:

``````• Both the users will first create and exchange their public keys among them.
• Both will consider Prime Number q as 43 and Primitive Root α as 5 to create their public keys
``````

Considering the above given information and assuming the Private Keys of User-1 and User-2 as 10 and 23 respectively, you are required to find the following:

``````1. Public Keys of Both the Users
2.  Common Secret Key
``````

Note: You need to apply the Algorithm for finding the Public Keys and Common Secret Key at both sides i.e., User-1 and User-2. Also, mention all necessary equations/formulas and calculation steps to give your answer.

Question No.2

Suppose a sender A wants to send a message “3” to a Receiver B by encrypting the message using RSA (Rivest–Shamir–Adleman) Algorithm. Assuming the Public Key PU of the sender A as {5,14} and Private Key PK of the receiver B as {11, 14}, you are required to perform encryption at the sender side to convert the given plain text into cipher text and perform decryption at the receiver side to convert the cipher text back into the plain text.

Note: You need to give your answer in the following table by writing all necessary calculation steps:

Encryption = Enc process goes here

Decryption = Dec process goes here

1

6

2

2

2

1

1

6
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