A type of digital chaotic cryptosystem was proposed which used a class of 1-D piecewise linear map to realize finite-precision chaotic encryption and decryption systems through the inverse system approach. In the general structure of encryption systems, a dynamical system /spl Sigma/ (/spl middot/) is used to connect the n-order delay line with the input terminal. The decoder is sensitive to all parameter mismatches, so it can provide high security of the encrypted signals. In this paper we show that this cryptosystem can not frustrate chosen-ciphertext attack. Consequently, it may be possible to recover the key with good accuracy.