Cloud Security Fundamental

1. What is a security mechanism used to counter a malicious intermediary?
2. With reference to picture below, why does CA need to encrypt the hash message with its private key (CAs private key)? What would happen if CA encrypted the hash with its public key?
3. Is a cloud consumers public key used to encrypt cloud consumer data? If yes, explain why does a consumer need to do that? If not, what is this public key for?

cloud consumer certificate cloud consumer cloud consumer data attested by CA cloud consumer's public key CA digital signature cloud cloud consumer's consumer's private key public key certificate properties certificate request hashing mechanism cloud consumer data cloud consumer's public key cloud consumer data hash A37EFFB1 CA digital signature cloud consumer's public key CA'S private key CA