[en] Recently, an image encryption cryptosystem based on binary bit planes extraction and multiple chaotic maps (IEC-BPMC) was proposed, which includes two main parts: bit-level permutation for high 4-bit planes and bit-wise XOR diffusion. Some security analyses and experimental simulations were presented to support it to resist various attacks. However, it is found that the diffusion and permutation parts can be cracked separately by the divide-and-conquer strategy due to its inherent pitfalls. Then the equivalent diffusion key and the equivalent permutation key can be recovered by the chosen-plaintext attack method. Both theoretical analysis and experimental results demonstrate that IEC-BPMC is insecure against chosen-plaintext attack with low data complexity and computational complexity. Moreover, some other security defects of IEC-BPMC are revealed. Finally, some suggestions for improvement are given to enhance the security.