On the Equivalency of Reliability and Security Metrics for Wireline   Networks
  In this paper, we show the equivalency of weak and strong secrecy conditions for a large class of secure network coding problems. When we restrict to linear operations, we show the equivalency of "perfect secrecy and zero-error constraints" with "weak secrecy and $\epsilon$-error constraints". 
Mohammad Mahdi Mojahedian, Amin Gohari, Mohammad Reza Aref
cs.IT math.IT