Você pode usar um argumento estrito e não trocar chaves entre clientes, em seguida, configurar os hosts e o firewall da estação de trabalho para não aceitar conexões da sub-rede de clientes.
StrictSubnets = yes | no (no) [experimental]
When this option is enabled tinc will only use Subnet statements which are present in the host config files in the
local /etc/tinc/NETNAME/hosts/ directory. Subnets learned via connections to other nodes and which are not present
in the local host config files are ignored.
TunnelServer = yes | no (no) [experimental]
When this option is enabled tinc will no longer forward information between other tinc daemons, and will only allow
connections with nodes for which host config files are present in the local /etc/tinc/NETNAME/hosts/ directory.
Setting this options also implicitly sets StrictSubnets.