Security is the most vulnerable part of any P2P system. In F2F we are bootstrapping P2P TCP communication using existing IM protocols (which are secure and authenticated by default). However the flexible communication layer of the F2F Computing allows to operate in TCP only (after successful bootstrap routine). In other words once the peer joined the private F2F group using his IM account, he is automatically connected to all the participants through TCP as well. Now if this new peer goes offline/online the P2P communication should be restored quickly without IM usage. Thanks to help of the Security Group of CS department we designed one possible solution and currently start implementing it.