Question

CAN BE BOTH SOLVED PLEASE

1)Suppose digital signature can be used to protect the integrity of the communications between Alice and Bob. Alice’s public key is e_A, private key is d_A; Bob’s public key is e_B, private key is d_B. Now Alice wants to send a message m to Bob. Describe the signature generation process, message components, and the signature verification process

2)Suppose message authentication code (MAC) can be used to protect the integrity of the communications between Alice and Bob. Suppose Alice and Bob already have a shared secret key k. Now Alice wants to send a message m to Bob. Describe the MAC generation process, message components, and the MAC verification process.

Answer 1

a)

this is for RSA digital signature. this can be applies to any digital signature scheme

alice create a digest of m to sign it.

alice sign it with dA and rsa engine generate signature

alice send both signed digest (SD) and message(m)

bob receive m and SD and generate a digest (SD1) from m

bob pass SD and eA to RSA engine which recovers digest.

bob compares SD and SD1. if found equal, accept it.

b)

alice uses K and pass message(m) to MAC algorithm to create MAC

alice send both MAC and (m)

bob receive m and MAC and generate a MAC1 from m using K

bob compares MAC and MAC1. if found equal, accept it.