The recent cryptanalysis on block ciphers has two major trends. Side channel analysis (SCA) has become a new threat to the hardware implementations of encryption algorithms. On the other hand, reverse engineering has been adopted to explore the unknown part of the encryption algorithms, which has become a new target of the cryptanalysis. Some drawbacks have been found in the existing methods of reverse engineering, which target on the special structures or utilize the flaws in the unknown parts. The major disadvantage is that the number of rounds to be analyzed is limited, and the complexity is high. The existing SCAs for reverse engineering depend on the leakage models in a large extent and mainly focus on the single component of the algorithms, whereas the other parts of the target algorithm are known. In this paper, we present a more general and feasible reverse analysis by combining the mathematical methods and the SCA methods. We use the strict avalanche criterion for the non-linear operations of block ciphers and apply the power analysis to reverse the structure parameters. We propose a new reverse analysis method to reduce the dependency on the leakage models, which can be combined with the structural cryptanalysis to reverse the internal parameters of the linear and non-linear operations. We finally achieve the reverse analysis on the unknown round function of block ciphers. Copyright © 2013 John Wiley & Sons, Ltd.