Let's think of the following case:
A group of peers want to exchange messages with each other. They use public-key cryptography to sign and encrypt messages. Anyone with any name can join the network. There is no central trusted authority, such as a CA that could issue certificates. When a peer joins, he publishes either, A) a self-signed certificate or B) a public key only, that others can use to him send messages.
Would under such circumstances cryptographic certificates (A) provide any advantage over using just private/public key pairs (B)? As far as I have understood certificates can only make sense if everyone trusts a central authority that issues certificates.
To my mind, that means if a peer joins the network it is sufficient that he broadcasts a message with his name+public key, signed with his private key. Everyone would know that he is in the posession of a private key for the specific public key.
That also implies that we cannot be sure a peer who claims to have a certain name really has this name. (Let's consider each peer has a name, that we don't know.)
What is your opinion about it?