In an RSA digital signature scheme, Bob signs messages xi and sends them together with the signatures si and her public key to Alice. Bob's public key is the pair (n,e); her private key is d. Oscar can perform man-in-the-middle attacks, i.e., he can replace Bob's public key by his own on the channel. His goal is to alter messages and provide these with a digital signature which will check out correctly on Alice's side. Show everything that Oscar must do for a successful attack.