Interpolation-based hiding scheme using the modulus function and re-encoding strategy

- This study improves Biswapati et al.'s scheme by using modulus function and re-encoding strategy.
- The proposed scheme reduces the value range of the position values and re-encodes the values to reduce the image distortion.
- A re-encode function is generated to obtain the rank of the position value in descending order.
- A mapping function is proposed to map the re-encoded code to the mapping code.
- The mapping code is half of the re-encoded code such that the image distortion becomes small.

Biswapati et al. proposed a interpolation-based hiding scheme. The scheme directly conceals the information, which records the position of the modified pixel to generate the stego-image. The position value is very large, thus creating a large image distortion. This study reduces the value range of the position values and re-encodes the values to reduce the distortion. The proposed scheme examines the probabilities for the position values and re-encodes the value according to its occurrence number. A re-encode function is used to obtain the rank of the position value in descending order. The most frequent position value is re-encoded to zero. The re-encoded codes are positive numbers, and the values of the codes are still large. To narrow down the value, the re-encoded codes are ciphered to generate mapping codes with negative and positive numbers. A mapping function is proposed to map the re-encoded code to the mapping code. The mapping code is half of the re-encoded code such that the image distortion becomes small. The proposed scheme uses different sizes of embedding blocks to control the hiding rate and image quality. Compared with other state-of-the-art methods, the proposed scheme is better in terms of hiding payload and image quality.