Encryption is used to securely transmit data in open networks. Each type of data has its own features, therefore different techniques should be used to protect conf idential image data from unauthorized access. Most of the available encryption algorithms are mainly used for textual data and may not be suitable for multimedia data such as images. In this paper, we introduce a block-based transformation algorithm based on the combination of image transformation and a well known encryption and decryption algorithm called Blowfish. The original image was divided into blocks, which were rearranged into a transformed image using a transformation algorithm presented here, and then the transformed image was encrypted using the Blowfish algorithm. The results showed that the correlation between image elements was sig nificantly decreased by using the proposed technique. The results also show that increasing the number of blocks by using smaller block sizes resulted in a lower correlation and hig her entropy.

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Image Encryption Using Block-Based Transformation Algorithm

Based on hyper-chaotic systems, a novel image encryption algorithm is introduced in this paper. The advantages of our proposed approach are that it can be realized easily in one round diffusion process and is computationally very simple while attaining high security level, high key sensitivity, high plaintext sensitivity and other properties simultaneously. The key stream generated by hyper-chaotic system is related to the original image. Moreover, to encrypt each pixel, we use the sum of pixels which are located after that pixel. The algorithm uses different summations when encrypting different input images (even with the same sequence based on hyper-chaotic system). This, in turn, will considerably enhance the cryptosystem resistance against known/chosen-plaintext and differential attacks. The change rate of the number of pixels in the cipher-image when only one pixel of the original image is modified (NPCR) and the Unified Average Changing Intensity (UACI) are already very high (NPCR?>?99.80233 % and UACI?>?33.55484 %). Also, experimental results such as key space analysis, histograms, correlation coefficients, information entropy, peak signal-to-noise ratio, key sensitivity analysis, differential analysis and decryption quality, show that the proposed image encryption algorithm is secure and reliable, with high potential to be adopted for the secure image communication applications.

A simple, sensitive and secure image encryption algorithm based on hyper-chaotic system with only one round diffusion process

Due to social networks, demand for sharing multimedia data is significantly increased in last decade. However, lower complexity and frequent security breaches on public network such as Internet make it easy for eavesdroppers to approach the actual contents without any hurdle. Many encryption algorithms has been developed by researchers to increase the security of such traffic and make it difficult for eavesdroppers to access actual data. However, these traditional algorithms increase the communication overhead, computational cost and also do not provide security against new attacks. These issues in recent algorithms motivate the researchers to further explore this area and proposed such algorithms which have lower overhead, more efficiency than the existing techniques and equip with requirements of next generations multimedia networks. To address all these issues and keeping in mind the future of next generation multimedia networks, we proposed a secure and light-weight encryption scheme for digital images. The proposed technique initially divide plaintext image in a number of blocks and correlation coefficients of each block are then calculated. The block with the maximum correlation coefficient values are pixel-wise XORed with the random numbers generated from a skew tent map based on a pre-defined threshold value. At last, the whole image is permuted via two random sequences generated from TD-ERCS chaotic map. Experimental results shows higher security via checking correlation, entropy, histogram, diffusion characteristic and key sensitivity of the proposed scheme.

Chaos based efficient selective image encryption

An efficient and robust image encryption scheme for medical applications

Diffusion-substitution based gray image encryption scheme

This paper proposes a new approach for image encryption using a combination of different permutation techniques. The main idea behind the present work is that an image can be viewed as an arrangement of bits, pixels and blocks. The intelligible information present in an image is due to the correlations among the bits, pixels and blocks in a given arrangement. This perceivable information can be reduced by decreasing the correlation among the bits, pixels and blocks using certain permutation techniques. This paper presents an approach for a random combination of the aforementioned permutations for image encryption. From the results, it is observed that the permutation of bits is effective in significantly reducing the correlation thereby decreasing the perceptual information, whereas the permutation of pixels and blocks are good at producing higher level security compared to bit permutation. A random combination method employing all the three techniques thus is observed to be useful for tactical security applications, where protection is needed only against a casual observer. Keywords— Encryption, Permutation, Good key, Combinational permutation, Pseudo random index generator.

/pdf/a-new-image-encryption-approach-using-combinational-4ugmaz7lll.pdf

A New Image Encryption Approach using Combinational Permutation Techniques

We describe an effective method for image encryption which employs magnitude and phase manipulation using carrier images. Although it involves traditional methods like magnitude and phase encryptions, the novelty of this work lies in deploying the concept of carrier images for encryption purpose. To this end, a carrier image is randomly chosen from a set of stored images. One dimensional (1-D) discrete Fourier transform (DFT) is then carried out on the original image to be encrypted along with the carrier image. Row wise spectral addition and scaling is performed between the magnitude spectra of the original and carrier images by randomly selecting the rows. Similarly, row wise phase addition and scaling is performed between the original and carrier images phase spectra by randomly selecting the rows. The encrypted image obtained by these two operations is further subjected to one more level of magnitude and phase manipulation using another randomly chosen carrier image by 1-D DFT along the columns. The resulting encrypted image is found to be fully distorted, resulting in increasing the robustness of the proposed work. Further, applying the reverse process at the receiver, the decrypted image is found to be distortionless. Keywords— Encryption, Carrier images, Magnitude manipulation, Phase manipulation.

An Image Encryption Method with Magnitude and Phase Manipulation using Carrier Images

We propose an effective approach for partial image encryption with pseudo random sequences (PRS). It is known that an image can be considered as a combination of correlated and uncorrelated data as well as most of the perceptual information are present in the correlated data rather than the uncorrelated data. Hence, the amount of residual intelligence present in an encrypted image depends on the correlated data. It is, therefore, sufficient to encrypt the correlated data instead of encrypting the entire image in order to speed up the entire operation. From the perception point of view, the most significant bit (MSB) planes have high adjacent correlation between the pixels whereas the least significant bit (LSB) planes contain comparatively more uncorrelated data. PRS with simple hardware like m-sequences and Gold sequences have less correlation between the adjacent bits. These can therefore serve as a good alternative for partially encrypting the MSB planes with low complexity to provide security against casual listeners. It is observed from the results that the new approach is able to reduce the residual intelligence as would have been obtained by encrypting the entire image.

A partial image encryption method with pseudo random sequences

One of the fundamental construction blocks in safeguarding group communications is group key establishment protocols. Group key agreement protocols are more suitable for distributed environments where the participant from various places can agree upon the group key. Group key related information is distributed to various group participants, mostly using techniques such as using polynomials, bilinear pairing, and secret sharing scheme (SSS). Out of these, secret sharing schemes are more efficient compared to other techniques. Recent growth in Internet of things (IoT) related applications stresses the need for such key agreement protocols in resource-constrained environments. Elliptic curves are quite popular in resource-constrained environments to produce enough security with smaller key sizes. Elliptic curve secret sharing scheme (ECSSS) is proposed in this paper for resource-constrained environments. Using the same scheme, Authenticated distributed group key agreement protocol using Elliptic curve secret sharing scheme (ADGKAP) is proposed, which can be used as a group key agreement protocol, and the group key related information is shared using ECSSS. To the best of our knowledge, we know no group key agreement protocol in the literature that uses ECSSS in a distributed environment. Our proposed ADGKAP provides equal security with less key size, storage space, faster computation, and less computational cost without compromising on the number of rounds compared to existing schemes. This scheme security relies on the Elliptic curve discrete logarithm problem (ECDLP), and the security analysis of the scheme is discussed.

Y. V. Subba Rao

Papers

A New Image Encryption Approach using Combinational Permutation Techniques

An Image Encryption Method with Magnitude and Phase Manipulation using Carrier Images

A partial image encryption method with pseudo random sequences

Authenticated Distributed Group Key Agreement Protocol Using Elliptic Curve Secret Sharing Scheme