No one, I think, argues that the granting of the keys is sufficient to properly define the exercise of the Office, but it sure defines the existence of the Office.
Just recently I was told that the keys were loaned, like a family sedan, to Peter and returned; or that they were also given St. John the Theologian and St. Paul. I am waiting for the next hypothesis, that in Greek "to give the keys" really means something derogatory, not unlike the recently discovered "you Peter, satanic pebble..." scripture.
As to the "keys of the kingdom" it appears they were given to the Apostles present" (post 65)
I am going to bed. Frankly, my dear Scarlet, I don't give a key.