Evaluation of the quality of an image encrytion scheme (original) (raw)

Encryption systems have been developed for image viewing applications using the Hill Cipher algorithm. This study aims to evaluate the image encryption quality of the Hill Cipher algorithm. Several traditional metrics are used to evaluate the quality of the encryption scheme. Three of such metrics have been selected for this study. These include, the Colour Histogram, the Maximum Deviation (comparing the original image) and the Entropy Analysis of the encrypted image. Encryption quality results from all three schemes using a variety of images show that a plain Hill Cipher approach gives a good result for all kinds of images but is more suited for colour dense images. 1. Introduction Encryption schemes [1-13] are only as good as the difficulty posed in attacking its results. This difficulty is a function of various factors dependent on the encryption scheme or method employed. With respect to images, the difficulty of retrieving an original image [14-16] from one that is ciphered is the clear objective in evaluating an encryption scheme's security and performance. Evaluation also helps in ascertaining that a good visual result is obtained for a variety of images whilst using an encryption scheme (encrypted images must leave nothing exposed from an original image). Another purpose of evaluating an encryption scheme is to improve the time performance of the encryption process whilst also ensuring that its result is not susceptible to any security attack. This study details the evaluation of the performance and security (quality) of an encryption scheme implemented using the Hill Cipher algorithm. A number of studies have shown that a visual inspection is insufficient to estimate correctly the quality of an encryption scheme [17]. A number of novel tests and analyses have been introduced and these tests have been classified into various categories. Notably, Li et al [18] classified objective evaluation into two namely: reference and non-reference objective evaluation. Objective evaluation is done with the reference or original image in use whilst a non-reference evaluation does not rely on the reference image. All evaluation however, border on measuring the randomness introduced to an image by an encryption scheme. It may also seek to show its vulnerability to security attacks. This study is organized as follows; section two gives an overview of quality metrics and the various types of tests and analyses that can be carried out on an encryption scheme. Section three discusses the implementation of the encryption quality interface. Section four outlines the results obtained for various image types. Section 5 concludes the study.