The growing of research interest in chaos and cryptography has resulted in a number of digital chaotic cryptographic approaches that realize private key cryptography with chaos.Among those chaotic cryptographic schemes,the one proposed by Baptista [1] has attracted much interest.Since its publication in 1998,a number of variants have been suggested.In particular,we have proposed a variant of the Baptista-type chaotic cryptosystem based on iterating the logistic map and updating the look-up table dynamically [2].However,it has been broken recently [3].In this presentation,the original dynamic look-up table scheme and its weaknesses are analyzed.Then a more secure chaotic encryption scheme based on this dynamic look-up table concept is proposed.