(a) Digital signature for large text message (Marks: 3) Assume that both Bob and Alice are connected to a free WiFi netw

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A Digital Signature For Large Text Message Marks 3 Assume That Both Bob And Alice Are Connected To A Free Wifi Netw 1 (113.22 KiB) Viewed 35 times

(a) Digital signature for large text message (Marks: 3) Assume that both Bob and Alice are connected to a free WiFi network. Suppose Bob (the sender) wants to send a large text message M to Alice (the receiver) using a message sharing application. As Bob and Alice are connected to free WiFi network, the communication is vulnerable to data modification attack performed by cyber attackers. In other words, a cyber attacker Trudy can capture a message M that is sent by Bob to Alice, modify M, and send modified message to Alice. Hence, Bob and Alice have decided to use digital signature to ensure the authenticity and integrity of the message. Say, Bob (sender) has a text message Mas follows (bold and italic faced text within two lines): Hi Alice, As we are using publicly available free WiFi network, our communication may be intercepted by cyber attackers. Therefore, we need to learn and apply cryptography techniques in our future communications. For now, I am just using RSA digital signature. Please verify my message once you receive it. Let's meet now at the RMIT library to discuss our study plan on cryptography. Sincerely, Bob Before sending the message, Bob generates a hash h(M) of the text message M using the MD5 hash algorithm and converts h(M) into integer message m. Then, he signs h(M) and sends M and signed h(M) to Alice. When Alice receives the signed h(M), she would like to verify if they are indeed from Bob and the message M is not altered. To facilitate signing and verification, Bob generates public and private keys using RSA encryption algorithm and sends the public key to Alice. Bob uses the following parameters: 1st Prime number: p = 645353605880701501120167331073 q=350784310265709643169455170929 2nd Prime number: Public key parameter: e = 19 In this task, you need to show how Bob generates digital signature for a large text message and Alice verifies the signature using RSA based digital signature scheme. To do this: i. show how Bob would generate Public and Private keys. different show how Bob would generate the digital signature for h(M). ii show how Alice would verify the digital signature using Bob's public-key. iv. Do you think that RSA based digital signature can be forged? Justify why or why not.