Finite-Blocklength Bounds for Wiretap Channels
  This paper investigates the maximal secrecy rate over a wiretap channel subject to reliability and secrecy constraints at a given blocklength. New achievability and converse bounds are derived, which are shown to be tighter than existing bounds. The bounds also lead to the tightest second-order coding rate for discrete memoryless and Gaussian wiretap channels. 
Wei Yang and Rafael F. Schaefer and H. Vincent Poor
cs.IT math.IT