  A two-phase beamforming solution for secure communication using untrusted
relay nodes is presented. To thwart eavesdropping attempts of relay nodes, we
deliberately introduce artificial noise in the source message. After pointing
out the incongruity in evaluating secrecy rate in our model for certain
scenarios, we provide an SNR based frame work for secure communication. We
intend to bring down the SNR at each of the untrusted relay nodes below a
certain predefined threshold, whereas, using beamforming we want to boost the
SNR at the destination. With this motive optimal scaling vector is evaluated
for beamforming phase which not only nullifies the artificial noise transmitted
initially, but also maximizes the SNR at the destination. We discuss both the
total and individual power constraint scenarios and provide analytical solution
for both of them.
