  We plan to simulate a private and unlinkable exchange of messages by using a
Public bulletin board and Mix networks in Opportunistic networks. This
Opportunistic network uses a secure and privacy-friendly asynchronous
unidirectional message transmission protocol. By using this protocol, we create
a Public bulletin board in a network that makes individuals send or receive
events unlinkable to one another . With the design of a Public bulletin board
in an Opportunistic network, the clients can use the benefits of this Public
bulletin board in a safe environment. When this Opportunistic network uses the
protocol, it can guarantee an unlinkable communication based on the Mix
networks. The protocol can work with the Public bulletin board exclusively with
acceptable performance. Also, this simulation can be used for hiding metadata
in the bidirectional message exchange in some messengers such as WhatsApp. As
we know, one of the main goals of a messenger like WhatsApp is to protect the
social graph. By using this protocol, a messenger can protect social graph and
a central Public bulletin board.
