On the Security of the Secure Arithmetic Code

In 2007, Kim et al. proposed a secure compression code called the secure arithmetic code (SAC). The code was claimed to be secure against chosen plaintext attacks. However, we find that the SAC is not as secure as the authors have claimed. In this paper, we show the code is prone to two attacks. The first attack completely breaks the code using an adaptive chosen plaintext attack with a polynomial number of queries. The second attack is a ciphertext-only attack, which removes a part of the output permutation.