# Encryption of 3D or Higher-Dimensional Images: A Review
###### Abstract  
This article aims to review encryption techniques for 3D or higher-dimensional images. Precisely, the following classes of images are considered: light field images, point clouds, and 3D medical images. The security and performance aspects of the encryption schemes for images are analyzed. It is observed that the number of papers with encryption in the transform domain exceeds the number of papers with encryption in the spatial domain. Additionally, it is observed that the application of encryption does not predominate in all the dimensions of the images, that is, the encryption does not occur completely in the image but rather through slices or sections. This review article summarizes several issues related to encryption techniques, technical perspectives for the future, and gaps in the literature.  
image encryption; 3D image; light field; point cloud +
Footnote †: journal: Applied sciences  
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or higher-dimensional images most used in the selected articles are light field images and point clouds.  
Because of the advancement in augmented reality techniques and applications, an increase in the number of papers focused on the encryption of 3D objects and holographic images has been observed, as explored in the following articles [14; 15; 16; 17; 18]. However, the scope of this review is the encryption of three-dimensional or higher-dimensional images. Precisely, the following classes of images are considered: light field images, point clouds, and 3D medical images.  
An encryption system needs to be secure even when the encryption algorithm is known. This assumes that attackers have full knowledge about the encryption and decryption methods used, but not about the cryptography key [19].  
Among the most common attacks, we can mention the brute force attack, in which there is an extensive search for all possible keys existing in the cipher, and the known plaintext, where the original image, the decrypted one, and the encryption technique used in the scheme are known, intending to discover the key used in the process [20].  
Thus, motivated by the above context, in the present paper a literature review is carried out on 3D or higher-dimensional image encryption. Articles were selected from the Web of Science platform, between the years 2019 and 2024.  
This review is expected to be useful for interested readers, engineers, computer scientists, or practitioners who study the methods for protection of three-dimensional or higher-dimensional images. Existing gaps in the literature and topics that deserve better attention are presented. It is worth mentioning that bibliometric information is presented in the paper.  
The rest of the article is organized as follows. In Section 2, we review concepts related to plenoptic images. Section 3 addresses the methodology used to survey the articles for the study. In Section 4, we address the main aspects of encryption methods. Our contributions and discussions are presented in Section 5, and finally, in Section 6, we conclude the article.