  Recently, three useful secrecy metrics based on the partial secrecy regime
were proposed to analyze secure transmissions on wireless systems over
quasi-static fading channels, namely: generalized secrecy outage probability,
average fractional equivocation, and average information leakage. These metrics
were devised from the concept of fractional equivocation, which is related to
the decoding error probability at the eavesdropper, so as to provide a
comprehensive insight on the practical implementation of wireless systems with
different levels of secrecy requirements. Considering the partial secrecy
regime, in this paper we examine the secrecy performance of an
amplify-and-forward relaying network with an untrusted relay node, where a
destination-based jamming is employed to enable secure transmissions. In this
regard, a closed-form approximation is derived for the generalized secrecy
outage probability, and integral-form expressions are obtained for the average
fractional equivocation and the average information leakage rate. Additionally,
equal and optimal power allocation schemes are investigated and compared for
the three metrics. From this analysis, we show that different power allocation
approaches lead to different system design criteria. The obtained expressions
are validated via Monte Carlo simulations.
