  We consider the problem of detecting clones in wireless mobile adhoc
networks. We assume that one of the devices of the network has been cloned.
Everything, including certificates and secret keys. This can happen quite
easily, because of a virus that immediately after sending all the content of
the infected device to the adversary destroys itself, or just because the owner
has left his device unattended for a few minutes in a hostile environment. The
problem is to detect this attack. We propose a solution in networks of mobile
devices carried by individuals. These networks are composed by nodes that have
the capability of using short-range communication technology like blue-tooth or
Wi-Fi, where nodes are carried by mobile users, and where links appear and
disappear according to the social relationships between the users. Our idea is
to use social physical contacts, securely collected by wireless personal
smart-phones, as a biometric way to authenticate the legitimate owner of the
device and detect the clone attack. We introduce two mechanisms: Personal Marks
and Community Certificates. Personal Marks is a simple cryptographic protocol
that works very well when the adversary is an insider, a malicious node in the
network that is part, or not very far, from the social community of the
original device that has been cloned. Community Certificates work very well
when the adversary is an outsider, a node that has the goal of using the stolen
credentials when interacting with other nodes that are far in the social
network from the original device. When combined, these mechanisms provide an
excellent protection against this very strong attack. We prove our ideas and
solutions with extensive simulations in a real world scenario-with mobility
traces collected in a real life experiment
