ENKRIPSI DAN DEKRIPSI CITRA MENGGUNAKAN METODE FRAKTAL

Enkripsi citra dengan metode fraktal adalah proses penyandian yang mengubah citra asli (plain image) menjadi citra yang tidak bisa dimengerti (cipher image) dengan menggunakan citra fraktal (fraktal image). Sedangkan dekripsi citra adalah proses sebaliknya yaitu mengubah cipher image menjadi citra asli. Citra fraktal yang digunakan pada penelitian ini adalah citra himpunan Mandelbrot z2 – c pada domain tertentu, dengan z adalah variabel komplek. Pertama, dibahas bagaimana enkripsi dan dekripsi citra warna menggunakan citra himpunan Mandelbrot dengan data domainnya dijadikan sebagai kunci(key). Proses enkripsi dilakukan dengan merubah setiap pixel dari citra asli yaitu merubah nilai bit ke-2 (0 menjadi 1 atau 1 menjadi 0) kemudian ditambahkan nilai warna dari citra fraktalnya sehingga diperoleh citra terenkrip. Sedangkan proses dekripsi adalah proses sebaliknya, yaitu setiap pixel dari citra terenkrip nilai warnanya dikurangi nilai warna dari citra fraktalnya kemudian dirubah nilai bit ke-2nya (0 menjadi 1 atau 1 menjadi 0) sehingga diperoleh citra hasil dekripsi yang diharapkan sama dengan citra asli. Kemudian, dibuat program komputer yang mampu melakukan enkripsi dan dekripsi citra warna menggunakan citra himpunan Mandelbrot, baik yang single fractal maupun multi fractal, dan selanjutnya dilakukan analisis terhadap hasil program. Citra hasil enkripsi dari 6 citra uji dianalisis dengan menentukan nilai NPCR dan UACI, dimana nilai NPCR semuanya 100% sedangkan rerata nilai UACI adalah 31,47%. Waktu enkripsi reratanya adalah 2.95 detik dan waktu dekripsi reratanya 2,89 detik. Citra hasil dekripsi mempunyai RMSE = 0 terhadap citra asli, hal ini menunjukkan bahwa citra hasil dekripsi sama persis dengan citra asli, sedangkan dari hasil nilai UACI dari beberapa data uji dan juga berdasarkan pengamatan secara visual didapat bahwa citra hasil enkripsi menggunakan multi fraktal sedikit lebih baik dibandingkan dengan single fraktal.

Multimedia Cryptosystem for IoT Applications Based on a Novel Chaotic System around a Predefined Manifold

Multimedia data play an important role in our daily lives. The evolution of internet technologies means that multimedia data can easily participate amongst various users for specific purposes, in which multimedia data confidentiality and integrity have serious security issues. Chaos models play an important role in designing robust multimedia data cryptosystems. In this paper, a novel chaotic oscillator is presented. The oscillator has a particular property in which the chaotic dynamics are around pre-located manifolds. Various dynamics of the oscillator are studied. After analyzing the complex dynamics of the oscillator, it is applied to designing a new image cryptosystem, in which the results of the presented cryptosystem are tested from various viewpoints such as randomness, time encryption, correlation, plain image sensitivity, key-space, key sensitivity, histogram, entropy, resistance to classical types of attacks, and data loss analyses. The goal of the paper is proposing an applicable encryption method based on a novel chaotic oscillator with an attractor around a pre-located manifold. All the investigations confirm the reliability of using the presented cryptosystem for various IoT applications from image capture to use it.

Cryptanalysis of an Image Encryption Algorithm Based on Random Walk and Hyperchaotic Systems

Recently, an image encryption algorithm based on random walk and hyperchaotic systems has been proposed. The main idea of the original paper is to scramble the plain image by means of random walk matrix and then to append diffusion. In this paper, the encryption method with security holes is analyzed by chosen plaintext attack. In addition, this paper improves the original encryption algorithm. The experimental and simulation results show that the improved algorithm has the advantages of the original and can improve the ability to resist attack.

Cryptanalysis of a New Chaotic Image Encryption Technique Based on Multiple Discrete Dynamical Maps

Recently, a new chaotic image encryption technique was proposed based on multiple discrete dynamic maps. The authors claim that the scheme can provide excellent privacy for traditional digital images. However, in order to minimize the computational cost, the encryption scheme adopts one-round encryption and a traditional permutation–diffusion structure. Through cryptanalysis, there is no strong correlation between the key and the plain image, which leads to the collapse of cryptosystem. Based on this, two methods of chosen-plaintext attacks are proposed in this paper. The two methods require 3 pairs and 258 pairs of plain and cipher images, respectively, to break the original encryption system. The simulation results show the effectiveness of the two schemes.

Correcting Errors in Color Image Encryption Algorithm Based on Fault Tolerance Technique

Security standards have been raised through modern multimedia communications technology, which allows for enormous progress in security. Modern multimedia communication technologies are concerned with fault tolerance technique and information security. As a primary method, there is widespread use of image encryption to protect image information security. Over the past few years, image encryption has paid more attention to combining DNA technologies in order to increase security. The objective here is to provide a new method for correcting color image encryption errors due to the uncertainty of DNA computing by using the fractional order hyperchaotic Lorenz system. To increase randomness, the proposed cryptosystem is applied to the three plain image channels: Red, Green, and Blue. Several methods were compared including the following: entropy, correlation, key sensitivity, key space, data loss attacks, speed computation, Number of Pixel changing rate (NPCR), and Unified Average Change Intensity randomness (UACI) tests. Consequently, the proposed scheme is very secure against a variety of cryptographic attacks.

Generalized multi-channel scheme for secure image encryption

The ability of metamaterials to manipulate optical waves in both the spatial and spectral domains has provided new opportunities for image encoding. Combined with the recent advances in hyperspectral imaging, this suggests exciting new possibilities for the development of secure communication systems. While traditional image encryption approaches perform a 1-to-1 transformation on a plain image to form a cipher image, we propose a 1-to-n transformation scheme. Plain image data is dispersed across n seemingly random cipher images, each transmitted on a separate spectral channel. We show that the size of our key space increases as a double exponential with the number of channels used, ensuring security against both brute-force attacks and more sophisticated attacks based on statistical sampling. Moreover, our multichannel scheme can be cascaded with a traditional 1-to-1 transformation scheme, effectively squaring the size of the key space. Our results suggest exciting new possibilities for secure transmission in multi-wavelength imaging channels.

An Image Encryption Algorithm Using Logistic Map with Plaintext-Related Parameter Values

This paper deals with a plaintext-related image encryption algorithm that modifies the parameter values used by the logistic map according to plain image pixel intensities. The parameter values are altered in a row-wise manner, which enables the usage of the same procedure also during the decryption. Furthermore, the parameter modification technique takes into account knowledge about the logistic map, its fixed points and possible periodic cycles. Since the resulting interval of parameter values achieves high positive values of Lyapunov exponents, the chaotic behavior of the logistic map should be most pronounced. These assumptions are verified by a set of experiments and the obtained numerical values are compared with those reported in relevant papers. It is found that the proposed design that uses a simpler, but well-studied, chaotic map with mitigated issues obtains results comparable with algorithms that use more complex chaotic systems. Moreover, the proposed solution is much faster than other approaches with a similar purpose.

Secure Image Authentication Scheme Using Double Random-Phase Encoding and Compressive Sensing

Double random-phase encoding- (DRPE-) based compressive sensing (CS) systems support image authentication for noisy images. When extending such systems to resource-constrained applications, how to ensure the authentication strength for noisy images becomes challenging. To tackle the issue, an efficient and secure image authentication scheme is presented. The phase information of the plain image is generated using DRPE and quantized into a binary image as the authentication information. Meanwhile, a sparser error matrix generated by the same plain image and vector quantization (VQ) image works as the input of CS. The authentication information and VQ indexes are self-hidden into the quantized measurements to construct the combined image. Then, it is permutated and diffused with the chaotic sequences generated from a modified Henon map. After decryption at the receiver side, the verifier can implement the blind authentication between the noisy decoded image and the reconstructed image. Supported by the detailed numerical simulations and theoretical analyses, the DRPE-CSVQ exhibits more powerful compression and authentication capability than its counterpart.

Deniable Authentication Encryption for Privacy Protection using Blockchain

Cloud applications that work on medical data using blockchain is used by managers and doctors in order to get the image data that is shared between various healthcare institutions. To ensure workability and privacy of the image data, it is important to verify the authenticity of the data, retrieve cypher data and encrypt plain image data. An effective methodology to encrypt the data is the use of a public key authenticated encryption methodology which ensures workability and privacy of the data. But, there are a number of such methodologies available that have been formulated previously. However, the drawback with those methodologies is their inadequacy in protecting the privacy of the data. In order to overcome these disadvantages, we propose a searchable encryption algorithm that can be used for sharing blockchain- based medical image data. This methodology provides traceability, unforgettable and non-tampered image data using blockhain technology, overcoming the drawbacks of blockchain such as computing power and storage. The proposed work will also sustain keyword guessing attacks apart from verification of authenticity and privacy protection of the image data. Taking these factors into consideration, it is determine that there is much work involved in providing stronger security and protecting privacy of data senders. The proposed methodology also meets the requirement of indistinguishability of trapdoor and ciphertext. The highlights of the proposed work are its capability in improving the performance of the system in terms of security and privacy protection.