  Utilizing complex dynamics of chaotic maps and systems in encryption was
studied comprehensively in the past two and a half decades. In 1989, Fridrich's
chaotic image encryption scheme was designed by iterating chaotic position
permutation and value substitution some rounds, which received intensive
attention in the field of chaos-based cryptography. In 2010, Solak \textit{et
al.} proposed a chosen-ciphertext attack on the Fridrich's scheme utilizing
influence network between cipher-pixels and the corresponding plain-pixels.
Based on their creative work, this paper scrutinized some properties of
Fridrich's scheme with concise mathematical language. Then, some minor defects
of the real performance of Solak's attack method were given. The work provides
some bases for further optimizing attack on the Fridrich's scheme and its
variants.
