This paper presents a novel modification of integer arithmetic code, which performs compression and encryption at the same time. It is quite different from the randomized arithmetic code (RAC), the interval splitting arithmetic code (ISAC), and the secure arithmetic code (SAC). In security, we apply the Pseudo-Random Bit Generator (PRBG) and the Secure Hash Algorithm (SHA-256) to construct the key vector. Each bit of the key vector known to both the encoder and decoder is used to determine whether the source intervals respectively allocated to each of the different symbols are needed to be adjusted prior to encoding each new symbol. Experimental results indicate that our proposed code does not compromise the coding efficiency.