Method and arrangement for enabling communications between an entity operating a network including a first user, and a second user includes sending a message from the first user to the entity informing the entity of identification information of the second user interested in joining the network, sending from the entity to the first user a key to allow the second user to communicate with the entity, providing a message from the first user directly to the second user containing the key, sending a message from the second user to the entity using the key, determining whether the key sent by the second user corresponds to the key provided by the entity to the first user, and if so enabling communications between the second user and the entity. The ability of the first user to obtain a key to enable the second user to join the network is time-limited.