Network technology improves distributed applications. The parties in distributed applications need to exchange secret information to perform a specific task. These parties form a specific group. The secret message exchanges in the group are likely to be message exchanges in a secret conference over a network. To perform the secret message exchange, one needs a common secret key to encrypt or decrypt messages. The basic idea behind our method is to pass a secret line through a published point. Any attacker who uses only one point can not recover the secret line. Only the party who knows two points of the secret line can recover the line. Based on this idea, we propose some new key exchange protocols and a message exchange protocol. The secret key established through the proposed method is a set of the secret points. Moreover, because the secret key is a set of secret points, it can support the dynamic behalf of a dynamic peer group that allows new parties to join and parties to leave the group.