Abstract—To transmit data securely between different parties, a variety of security approaches have been proposed in the literature. Specifically, DNA based cryptography and steganography approaches were used to secure data transmission. In this paper, a substitution-based method for data hiding in DNA sequences is proposed. In the proposed data hiding method, data is encoded using a binary coding rule then the data is hidden into a DNA sequence. The proposed method provides an enhancement on a previously proposed DNA substitution method named Least Significant Base method. The proposed enhancement is based on a simple idea that, to the best of our knowledge, was not applied before. It was noticed that the DNA Amino acids can be organized into groups where each DNA codon in one of the groups can be used to encode two bits of the hidden message rather than only one bit as proposed by the Least Significant Base method. Like the Least Significant Base method, the proposed method is blind, preserves the DNA original biological structure in the fake DNA sequence and provides no expansion in the DNA sequence. The proposed method is evaluated using a public DNA sequences dataset named BALIBASE. The evaluation results showed that the proposed method achieved about 50% increase in the data hiding capacity when compared with the Least Significant Base method. Moreover, the results showed that the proposed method resulted in significant decrease in the cracking probability of the Least Significant Base method.