  This paper investigates on the problem of combining routing scheme and
physical layer security in multihop wireless networks with cooperative
diversity. We propose an ad-hoc natured hop-by-hop best secure relay selection
in a multihop network with several relays and an eavesdropper at each hop which
provides a safe routing scheme to transmit confidential message from
transmitter to legitimate receiver. The selection is based on the instantaneous
channel conditions of relay and eavesdropper at each hop. A theoretical
analysis is performed to derive new closed form expressions for probability of
non-zero secrecy capacity along with the exact end to end secrecy outage
probability at a normalized secrecy rate. Furthermore, we provide the
asymptotic expression to gain insights on the diversity gain.
