At the time of Peter's confession, who knew that Jesus was Messiah?

In the synoptic gospels, Peter acknowledges that Jesus is the Messiah. > Matthew 16:15-17 (NASB) He said to them, “But who do you say that I am?” Simon Peter answered, “You are the Christ, the Son of the living God.” And Jesus said to him, “Blessed are you, Simon Barjona, because flesh and blood did not reveal this to you, but My Father who is in heaven. > > Mark 8:27–30 (NASB) Jesus went out, along with His disciples, to the villages of Caesarea Philippi; and on the way He questioned His disciples, saying to them, “Who do people say that I am?” They told Him, saying, “John the Baptist; and others say Elijah; but others, one of the prophets.” And He continued by questioning them, “But who do you say that I am?” Peter *answered and *said to Him, “You are the Christ.” And He warned them to tell no one about Him. > > Luke 9:18–21 And it happened that while He was praying alone, the disciples were with Him, and He questioned them, saying, “Who do the people say that I am?” They answered and said, “John the Baptist, and others say Elijah; but others, that one of the prophets of old has risen again.” And He said to them, “But who do you say that I am?” And Peter answered and said, “The Christ of God.” But He warned them and instructed them not to tell this to anyone, It was apparently a secret, and Jesus instructed his disciples not to tell anyone. According to the chronology given by the synoptic gospels, other than those present at that moment, who was in on the secret?