# Quantum Image Steganography Schemes for Data Hiding: A Survey
## 4 Discussion  
Thus far, we have explored ten of the recently proposed schemes for applying quantum image steganography. Among all the schemes discussed in this paper, there are two main domains that exist in the classical and quantum steganography fields. The first is the spatial domain, which explains using data components to embed the secret data in it, and in this case, the image's pixels were used as a hiding place for embedding secret images [43]. While in the transform domain, the image is converted from the spatial to frequency domain, embedding the secret data into the image's wavelets [44]. As mentioned above, based on both the image's nature and hosting places, the techniques of image steganography encoding are grouped into two popular divisions, one of which is the spatial domain. This class (also known as the map domain) uses bit insertion and bit-wise operation to hide data directly when converting an image's pixel values[45]. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Scheme** & **Methodology** & \multicolumn{2}{c}{**Recent Outcomes**} & **Limitations** \\ \hline \multirow{6}{*}{Quantum Image Scrambling [14]} & Scrambles a piece of quantum media using the Hilbert scrambling protocol to produce a hidden disordered outcome before sending it to the receiver. & \multirow{6}{*}{*} & Applied quantum scrambling protocol into the hidden image prior to the embedding process to increase security and confidentiality. & It is more robust and offers less of a bit error rate than other techniques, but its channels could still image into the cover image to achieve robustness and increase the scheme’s security. & \multirow{6}{*}{It is more robust and offers less of a bit error rate than other techniques, but its channels could still be affected by noise during data transmission.} \\ \cline{1-1}  & Based on the original matrix coding approach which employs the Hamming code and wet-paper code to achieve steganography. & \multirow{6}{*}{*} & \multirow{6}{*}{Created two advanced protocols based on the double-layer matrix coding approach, which both achieved superior embedding capacity and efficiency.} & As it utilizes the idea of wet paper code, it only modifies a selective number of pixel blocks and not all of them after embedding secret information in the first embedding channel. \\ \hline \multirow{6}{*}{Interpolation- Based Scheme [12]} & Upscales the cover image using the interpolation algorithm and finding the difference between the new and original image to decide the number of bits to be embedded in each pixel. & \multirow{6}{*}{*} & Produced steganographic images with a superior image quality. & The algorithm used can be perceived as high in time complexity, making it slower in performance compared to other schemes. \\ \hline \multirow{6}{*}{CAQWs [10]} & A quantum alternative of the random walks protocol to choose locations in a random manner through a probability distribution matrix. & \multirow{6}{*}{Used CAQWs protocol to detect LSB embedding locations to hide quantum images into a cover image, achieving strong security and high resistance to data hazards.} & In some situations, processing a huge collection of images with good visual quality, resistance to data loss hazards, and high embedding capacity might not be granted \\ \hline \multirow{6}{*}{EMD [17]} & Hides a piece of media into a cover by embedding each qubit using the odd base carrying system. & \multirow{6}{*}{Enhanced the quantum EMD approach by expanding the modification range of the carrier image pixels to produce better imperceptibility.} & The embedding rate and capacity gradually decline as the group size increases, so there is a limit for how large it can become. \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \cline{1-1}  & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._It is considered popular due to the advantages it offers. For instance, the spatial domain grants lower computational complexity than the transform domain.