Date of Award

16-5-2024

Document Type

Thesis

School

School of Electrical & Electroncis Engineering

Programme

Ph.D.-Doctoral of Philosophy

First Advisor

Dr.R.Amirtharajan

Keywords

Reversible Steganography, Medical Image Security, Cryptography, Data Security, Information Hiding

Abstract

Electronic clinical data such as Patient Health Information (PHI) is stored by adapting the Digital Imaging and Communications in Medicine (DICOM) standard to build an integrated healthcare system where medical images from various sources can be interlinked. The healthcare industry poses a threat from hackers, and the information fetched by hackers provides more money than the other information stolen. This thesis deals with designing and analysing encryption algorithms, key generation mechanisms, and information-hiding schemes for protecting PHI.

Sensitive multimedia information of all forms is encrypted, with a key, before storage and transmission to protect it from illegal use and manipulation of data. Since digital images are more significant, effectively encrypting the content, specifically medical images, is crucial. Even a little data manipulation in medical image diagnosis may lead to misinterpretation. For this, an algorithm is devised to be suitable for encrypting DICOM and other images.

With the onset of any pandemic, the medical image database is bound to increase. These medical images are prone to attack by hackers for their medical data and PHI. To safeguard these medical images, a new algorithm is proposed. The algorithm involves secretly embedding the patient identification number into the medical image and encrypting the medical image, protecting the patient's identity and medical condition from hackers. The encryption algorithm involved a single stage of confusion and two stages of diffusion. The confusion operation was performed using the key generated by the Bülban map. The first stage of diffusion was done in the transform domain, using 5/3 transformation, and the second stage of diffusion was performed in the spatial domain by altering the pixel values using the key.

Transferring multimedia content without detection is gaining traction over a while. Using Steganography to hide secret data, viz. passwords, medical information, and secret messages, has become the norm. This work involves hiding confidential information in the images. It aims to increase the payload capacity by adaptively choosing the embedding pixel location, using hamming distance, and increasing the number of bits embedded per pixel using threshold while retaining the image quality. The embedding of secret information is random, using a key, generated using a Combined Logistical Tent Map, governed by equations and reordered using a Cartesian product generator. The algorithm is designed to perform embedding for images of various modalities, viz., Grayscale, RGB and DICOM.

The impact of hacking into medical images for PHI reverberates through the hospitals and their services. The need for PHI protection gives rise to the requirement of a practical algorithm for hiding the PHI within the medical image and recovering both PHI and the cover medical image. In this work, an adequate reversible data hiding using Bicubic Spline Interpolation, pixel value differencing, and adaptive data hiding is designed.

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