Author ORCID Identifier

https://orcid.org/0000-0001-6441-0402

Date of Award

11-3-2025

Document Type

Thesis

School

School of Electrical & Electroncis Engineering

Programme

Ph.D.-Doctoral of Philosophy

First Advisor

Dr.J.Siva

Keywords

Engineering, Medical Image Security, FPGA, Concurrent Cryptosystem, Cryptanalysis

Abstract

The protection of medical image privacy plays a crucial role in maintaining confidentiality for the secure storage and transmission of patient’s sensitive healthcare data. Medical images are the widely used data type in the e-healthcare sector. Traditional cryptographic algorithms have limitations when applied to large-scale medical image datasets due to their high computational requirements. The primary goal of this research work is to design and implement indigenous algorithms to provide confidentiality for grayscale and color DICOM (Digital Imaging and Communications in Medicine) images through an encryption process. The research leverages the benefits of reconfigurable hardware, namely the Field-Programmable Gate Arrays (FPGAs), to accelerate cryptographic operations through concurrent processing to maximize the hardware throughput.

Confusion and diffusion are the major operations for any cryptographic algorithm. This work proposes an edge detection process using the Sobel mask algorithm as a novel attack mechanism to cryptanalyse the encrypted images from confusionless cryptography schemes. A grayscale lightweight image encryption scheme was designed and implemented on FPGA using a robust diffusion unit utilising the random keys generated by the Lorentz attractor. This work aimed to arrive at an optimal number to achieve block-level concurrency on FPGA by dividing the 256×256 DICOM input image into distinct blocks.

This technique achieved a throughput of 200 Mbps per concurrent block, consuming only 3% of Logic Elements (LEs) with a minimal power dissipation of 138.85 mW under the optimal block count of 4. Another scheme for the encryption of color DICOM images with concurrency among the encryption of Red (R), Green (G), and Blue (B) planes was achieved with substitution boxes constructed using the Zhongtong chaotic system. The RGB cryptosystem offered a significantly expanded keyspace of 2912, a reduced resource utilization of 2212 LEs, and a minimal power consumption of 131.40 mW.

An additional layer of security for exchanging encrypted medical images between Xilinx PYNQ-Z1 SoC boards with incorporated integrity checks through encrypted hash values obtained through a whirlpool hashing scheme has been proposed. To ease the hash generation, hash encryption/decryption, and transmission/reception processes on the sending/receiving device, a user-friendly graphical user interface (GUI) was designed under the jupyterlab platform.

The proposed grayscale and color encryption schemes were developed using Verilog HDL code and implemented on the Intel Cyclone IV FPGA, utilizing less than 3% of available resources, making it a lightweight solution with significantly lower resource utilization compared to similar hardware-based encryption schemes reported in the literature.

The FPGA operated at a frequency of 50 MHz in the Quartus-II Integrated Development Environment (IDE). The developed concurrent cryptosystems were evaluated with a comprehensive set of performance metrics, including throughput, resource utilization, and power dissipation on FPGA. The security strength of the proposed medical image security schemes was analysed through various statistical metrics, including the NIST test suite.

Further, attack mechanisms such as Chosen Plain Text (CPT) and the proposed edge detection attacks assured the quality of encrypted images. This research has significant implications for protecting medical image privacy and the secure exchange of medical images with integrity verification, contributing to the advancement of a secure healthcare system.

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