  In recent years, a growing number of cryptosystems based on chaos have been
proposed, many of them fundamentally flawed by a lack of robustness and
security. This paper describes the security weaknesses of a recently proposed
cryptographic algorithm with chaos at the physical level. It is shown that the
security is trivially compromised for practical implementations of the
cryptosystem with finite computing precision and for the use of the iteration
number n as the secret key. Some possible countermeasures to enhance the
security of the chaos-based cryptographic algorithm are also discussed.
