Hiding data in parity check bit

In this paper, we propose a method to hide secret data in parity check bits. In the data embedding phase, the method first takes 4 bits from the cover data and 3 bits from the secret data. The 3-bit secret data are inserted into appropriate positions that represent the parity bits of the 4-bit cover data to form a code word. The Matrix Coding is then used to select a specific bit from the code word to modify so that the code word can satisfy the condition of (7, 4) Hamming code and the 4-bit stego data can be obtained. If the selected bit is a data bit, it is directly modified. In this case, the three parity check bits of the 4-bit stego data are exactly the 3-bit secret data. However, if the selected bit is a parity check bit of the code word, instead of modifying the parity check bit, two cover data bits are modified. In the data extracting phase, the 3-bit secret data can be extracted by calculating parity check bits of 4-bit stego data. The experimental results show that the proposed method has achieved comparable embedding capacity, and the number of modified pixels is also satisfactory.