A REVIEW OF DIGITAL IMAGE ENCRYPTION: SCAN-PATTERN METHODS, CRYPTOGRAPHY, COMPRESSION AND HARDWARE ACCELERATION

Abstract

The rapid growth of digital imaging, multimedia communication, medical information systems, remote sensing, surveillance and embedded vision has increased the need for reliable protection of image data. Unlike conventional textual data, digital images contain substantial redundancy and strong spatial relationships between neighboring pixels. These characteristics create both challenges and opportunities for cryptographic design. Consequently, numerous image-encryption techniques have been proposed using permutation, substitution, chaotic transformations, scan patterns, XOR operations, compression and hardware acceleration. This review critically examines three supplied studies representing complementary aspects of image security: a scan-pattern and XOR-based image-encryption method, a general study of cryptography, encryption and compression, and an FPGA-oriented approach to image processing and secure transmission. The hardware-oriented study demonstrates the feasibility of implementing image-processing operations and encrypted transmission on FPGA platforms, while the cryptography and compression study emphasizes confidentiality, authentication, integrity and efficient data representation. This review further considers contemporary authenticated-encryption approaches, including AES-GCM and ChaCha20-Poly1305, and discusses why statistical randomness alone cannot establish cryptographic security. The analysis identifies important research gaps involving authenticated encryption, key management, nonce handling, reproducibility, hardware security and resistance to realistic attack models.