Osama S. Farag Allah

Encryption quality analysis of the RC5 block cipher algorithm for digital images

We investigate the implementation and application of the RC5 block cipher algorithm for digital images and provide testing, verification, and encryption efficiency of the RC5 block cipher for digital images. We describe briefly the basic design parameters of the RC5 block cipher and its implementation for digital images. A complete specification for the method of application of the RC5 block cipher to digital images is given. Several test images are used for inspecting the validity of the encryption and decryption algorithms. Also, we provide and introduce a mathemati- cal measure for encryption efficiency, which we will call the encryption quality instead of visual inspection, and apply it to several images. The encryption quality of the RC5 block cipher algorithm is investigated along its several design parameters, such as word size, number of rounds, and secret key length, and the optimal choices for the best values of these design parameters are given.

Homomorphic image encryption

This paper presents a new homomorphic image cryptosystem. The idea of this system is based on encrypting the reflectance component after the homomorphic transform and embedding the illumination component as a least significant bit watermark into the encrypted reflectance component. A comparison study is held between the RC6 block cipher algorithm and the chaotic Baker map algorithm for the encryption of the reflectance component. We present a security analysis for the proposed cryptosystem against the entropy, brute-force, statistical, and differential attacks from a strict cryptographic viewpoint. Experimental results verify and prove that the proposed homomorphic image cryptosystem is highly secure from the cryptographic viewpoint. The results also prove that this cryptosystem has a very powerful diffusion mechanism (a small change in the plain text makes a great change in the cipher image). The homomorphic encryption using RC6 algorithm is more secure than that using the chaotic Baker map algorithm but not robust to noise. Thus, the proposed homomorphic cryptosystem can be used in different applications, depending on the core algorithm used.

Image fusion based on principal component analysis and high-pass filter

Several commercial earth observation satellites carry dual-resolution sensors, which provide high spatial resolution panchromatic image and low spatial resolution multi-spectral image. Image fusion techniques are therefore useful for integrating a high spectral resolution image with a high spatial resolution image, to produce a fused image with high spectral and spatial resolutions. Some image fusion methods such as IHS, PC and BT provide superior visual high-resolution multi-spectral images but ignore the requirement of high-quality synthesis of spectral information. The high-quality synthesis of spectral information is very important for most remote sensing application based on spectral signatures, such as lithology, soil and vegetation analysis. Another family of image fusion techniques such as HPF operates on the basis of the injection of high-frequency components from the high spatial resolution panchromatic image into the multi-spectral image. This family of methods provides less spectral distortion. In this paper we propose to integrate between the two families PCA and HPF to provide pan sharpened image with superior spatial resolution and less spectral distortion. The experiments have shown that the proposed fusion method retains the spectral characteristics of the multi-spectral image and improves at the same time the spatial resolution of the fused image.

An optimized Kerberos authentication protocol

This paper will introduce simple modifications to the database of the widely deployed Kerberos authentication protocol. The principles long-term secret key will be independent of the user password with the aim to overcome the weak passwords chosen by the network principal that are susceptible to password guessing attacks, the main drawback of the Kerberos protocol. Instead, the Kerberos Distribution Center will save a profile for every instance in the realm that it mange and the secret key will be generated based on that profile. This profile will be hashed and then, the output digest will be encrypted to generate the secret key. Besides, the lifetime of the secret key will be controlled using the system lifetime. We will use Triple-Des as an encryption algorithm, SHA-256 as a hashing algorithm, and Blum Blum Shub as a random number generator algorithm.

A new diffusion mechanism for data encryption in the ECB mode

In this paper, a diffusion mechanism for encrypting data in the electronic code book (ECB) mode is introduced. Our diffusion mechanism treats the encryption leakages of the ECB mode by using a substitution/permutation network (SPN), which diffuses the bytes of the data together before encryption. The tests were made on AES and RC6 block ciphers implemented in the ECB mode pre-processed with our mechanism and the results were compared to those obtained by these ciphers implemented in the ECB, cipher block chaining mode (CBC), cipher feedback (CFB) and output feedback (OFB) modes. Experimental results verify that this mechanism gives any encryption algorithm implemented in the ECB mode the ability to encrypt the data in a better efficiency than the CBC mode without losing the benefits of the ECB mode of parallel processing provided by processing powers nowadays.