Line map, an invertible, two-dimensional chaotic encryption algorithm was introduced recently. In this paper, we propose several weaknesses of the method based on standard cryptanalytic attacks. We perform a side-channel attack by observing the execution time of the encryption algorithm and successfully reduce the key space by a factor of 10^4 for a key length of 16 digits. We find the existence of equivalent keys which reduce the key space by a significant margin, even in the absence of any attack. Also, we find that the ciphertext is not sensitive to small changes in the plaintext due to poor diffusion.
N. Balaji and Nagaraj, N., “Cryptanalysis of a Chaotic Image Encryption Algorithm”, arXiv preprint arXiv:0801.0276, 2008.