Trusting a nod and sharing node

Hi all ,

I want some help in IPFS about trust a node and sharing file .

  1. How would we trust node that it is the node which he is claiming .(some one can say I am john it will create peer Id of john and public key but it is really john or not may be it is boby) how will get assurance that person we
    are dealing is the right person.
  2. as if we are using GPG for encryption file with person but how if I want to share a file more then one person
    in normal scenario I have to encrypt the file with public key of person I want to share the file.
  3. How it can safe from Man in the middle attack like someone in the middle intercept the communication and send his public keys and then decrypt it with his private key.