  Recently, a chaotic image encryption algorithm based on information entropy
(IEAIE) was proposed. This paper scrutinizes the security properties of the
algorithm and evaluates the validity of the used quantifiable security metrics.
When the round number is only one, the equivalent secret key of every basic
operation of IEAIE can be recovered with a differential attack separately. Some
common insecurity problems in the field of chaotic image encryption are found
in IEAIE, e.g. the short orbits of the digital chaotic system and the invalid
sensitivity mechanism built on information entropy of the plain image. Even
worse, each security metric is questionable, which undermines the security
credibility of IEAIE. Hence, IEAIE can only serve as a counterexample for
illustrating common pitfalls in designing secure communication method for image
data.
