Suppose Bob and Alice, two business partners, use their smartphones to communicate with each other regarding their business decisions. Hence, their messages are very sensitive and require to be authenticated. Otherwise, an attacker, say one of their business rivals, may perform phone number porting fraud attack. In this attack, the attacker may use another SIM card to port Alice or Bob's phone number for pretending as Alice or Bob, respectively. Therefore, Bob and Alice use a digital signature scheme in their smartphone to sign messages for ensuring authenticity. The working procedure of the digital signature is Illustrated in FigureQ2.

Answer the question Q1 by using the scenario mention above,

Q1

Suppose Bob (the sender) wants to send a message or-654321 to Alice (the receiver). However, before sending the message he would like to sign the message. When Alice receives the signed message, she would like to verify that the message is indeed from Bob. To facilitate signing and verification Bob generates public and private keys using the RSA encryption algorithm and sends the public key to Alice. Bob uses parameter p = 9973 and ci = 7541, and chooses a suitable public key parameter e=7321. How would Bob sign message m:654321? How would Alice verily the signed message from Bob?

Bob (Sender) Alice (Receiver) Message Verified Message Signing with Bob's private-key Verification with Bob's public-key A Signed Message Verification