Littérature scientifique sur le sujet « INVERSION-ENCRYPTION METHOD »

Color image encryption has enticed a lot of attention in recent years. Many authors proposed a chaotic system-based encryption algorithms for that purpose. However, due to the shortcomings of the low dimensional chaotic systems, similar rule structure for RGB channels, and the small keyspace, many of those were cryptanalyzed by chosen-plaintext or other well-known attacks. A Security vulnerability exists because of the same method being applied over the RGB channels. This paper aims to introduce a new three-channel three rules (3C3R) image encryption algorithm along with two novel mathematical models for DNA rule generator and bit inversion. A different rule structure was applied in the different RGB-channels. In the R-channel, a novel Block-based Bit Inversion (BBI) is introduced, in the G-channel Von-Neumann (VN) and Rotated Von-Neumann (RVN)- based 2D-cellular structure is applied. In the B-channel, a novel bidirectional State Machine-based DNA rule generator (SM-DNA) is introduced. Simulations and results show that the proposed 3C3R encryption algorithm is robust against all well-known attacks particularly for the known-plaintext attacks, statistical attacks, brute-force attacks, differential attacks, and occlusion attacks, etc. Also, unlike earlier encryption algorithms, the 3C3R has no security vulnerability.

This paper introduces a novel image encryption scheme based on chaotic maps and toggle cellular automata (TCA). In confusion stage, the proposed scheme utilizes logistic map to construct a nonlinear sequence for scrambling the plain-image. Then in diffusion stage, TCA is constructed by setting up the inversion rule and the image which has been processed by chaotic sequence is encryption again by using the TCA iteration method. Theoretical analysis and experimental results demonstrate the proposed algorithm achieves a high security level and processes good performance against common attacks like differential attack and statistical attack.

An encryption system that combines compressive sensing (CS) and two-step parallel phase shifting digital holography (PPSDH) using double random phase encoding (DRPE) is presented in this paper. The two-step PPSDH is a linear inline holographic scheme and is much suitable for encrypting the 2D/3D information in a single exposure. The distribution of random phase mask (RPM) in the DRPE is implemented using circular harmonic key which increases the security of the encryption process. In this system, the keys used to encrypt are spatial positions of the planes, wavelength, and rotation of the circular harmonics in RPMs, and CS acts as an additional key that makes the system more secure than the conventional optical encryption methods. At the transmission end, two-step PPSDH is applied to encrypt the object information in single hologram. The digital mirror device (DMD) is placed between the object and a single-pixel detector for acquiring fewer hologram measurements. At the receiver end, the single digital hologram is numerically recovered by using a CS optimization problem. The original complex object field is decrypted from the CS recovered holograms by the inversion of two-step PPSDH process with the help of the correct keys. The numerical simulations are presented for complex 2D and 3D objects to test the feasibility of the proposed encryption and decryption system. The proposed method carried out intensity and phase reconstruction of the original object field using single-pixel compressive imaging. The computer simulation results demonstrated that the encrypted information is highly secured with the rotation of the circular harmonic key. The sensitivity of the decrypted intensity and phase images is also studied with variations of the encrypted keys. The obtained results show that the proposed encryption scheme is feasible and has better security performance and robustness.

The role of substitution boxes is very important in block ciphers. Substitution boxes are utilized to create confusion in the cryptosystem. However, to create both confusion and diffusion in any cryptosystem p-boxes and chaos base substitution boxes are designed. In this work, a simple method is presented that serves both ways. This method is based on composition of the action of symmetric group on Galois field and inversion map. This construction method provides a large number of highly non-linear substitution permutation boxes having the property of confusion as well as diffusion. These substitution permutation boxes have all the cryptography properties. Their utilization in the image encryption application is measured by majority logic criterion. We named these newly designed substitution boxes (S-boxes) as substitution permutation boxes (S-p-boxes), because they serve as both substitution boxes (S-boxes) as well as permutation boxes (p-boxes).

Since entering the era of big data, the degree of information sharing is getting higher and higher; the information exchange is becoming more and more convenient, but at the same time, personal information is also easy to be exposed to the network environment, if it is used by criminals to lead to information leakage, and then bring certain risks. Therefore, it is in the information age and do a good job of network information security and confidentiality. At present, the security and secrecy of network information are mainly realized by cryptography. Public key cryptography can encrypt information and ensure the security of information transmission, so it is widely used in the contemporary society. At present, elliptic curve encryption is highly respected in the research field of public key cryptosystem. Elliptic curve encryption is divided into two main points, multiplication and inversion, respectively. Through the comparison of these two algorithms, it can be found that there are several choices if the main research objective is to save time, and the Euclidean extension method is mainly discussed in this paper. In other words, more efficient algorithms are used in the hardware implementation process, and a variety of algorithms can be used instead of a single curve algorithm. In this process, we can find the special features of upper level operation and bottom level finite operation. The upper level operation is KP operation, while the bottom level operation is fast calculation of four kinds of K in finite field operation, and finally realize FPGA algorithm. With the help of Quartus ii developed by predecessors, the upper and lower operations of elliptic curve are carried out using VHDL language. Combined ANXIX9.62 in the elliptic curve of each module to test, so as to ensure the accuracy of the data, reduces the error. According to the test results, the designed chip can efficiently complete the elliptic curve encryption system in the whole process. And the average KP operation time can reach 15.15 ms at 20 MHz frequency. At the same time, the chip can complete the operation on ECC public key with any variable curve in F domain less than 256. Therefore, this chip is a high-speed elliptic curve cryptographic chip with optional system parameters. Based on this, this article on the elliptic curve encryption algorithm based on FPGA hardware implementation of system design, from the view of mathematical study analysis, was carried out on the elliptic curve cryptosystem, according to the above two big difficulty, namely, the polynomial of GF(2), the finite field multiplication, and inversion; there will be a detailed studies of discussion, through software comparison to find the differences between different software, especially the software implementation performance level. In addition, it will also focus on the design of elliptic curve algorithm PGA, so as to explore the solution of the algorithm hardware.

<abstract><p>In this paper, fast numerical methods for solving the real quasi-symmetric Toeplitz linear system are studied in two stages. First, based on an order-reduction algorithm and the factorization of Toeplitz matrix inversion, a sequence of linear systems with a constant symmetric Toeplitz matrix are solved. Second, two new fast algorithms are employed to solve the real quasi-symmetric Toeplitz linear system. Furthermore, we show a fast algorithm for quasi-symmetric Toeplitz matrix-vector multiplication. In addition, the stability analysis of the splitting symmetric Toeplitz inversion is discussed. In mathematical or engineering problems, the proposed algorithms are extraordinarily effective for solving a sequence of linear systems with a constant symmetric Toeplitz matrix. Fast matrix-vector multiplication and a quasi-symmetric Toeplitz linear solver are proven to be suitable for image encryption and decryption.</p></abstract>

Aim: The aim of the paper is to analyse the security strength of image encryption schemes which are based on pixel rotation and inversion functions. The key independent image decryption methodologies are presented to obtain original images with intelligible contents from encrypted images using neighbourhood similarity characteristics and divide-and-conquer attack. Background: The efficiency and security strength of secure communication of sensitive data depends on the computing resources and cryptographic strength of encryption schemes. An encryption scheme is cryptographically strong if it does not leave any weakness, vulnerability or pattern which could be exploited by cryptanalyst to obtain original image from an encrypted image. Prior to use of any image encryption scheme for multimedia security applications, it should be analysed for its security strength to ensure the safety of information so that an adversary could not extract intelligible information from encrypted image data. A number of encryption schemes developed for image security applications and claimed highly secure but some of these are cryptanalyzed and found insecure. Objective: The analysis of image ciphers which encrypt plain images by transforming its pixels using circular rotation or inversion function in a random fashion is carried out to decrypt encrypted images to obtain original images. The encryption schemes, namely ‘Chaotic Image Encryption (CIE)’ and ‘Graphical Image Encryption (GIE)’, were reported secure but we find that these schemes are insecure and meaningful information can be obtained. We exploit image similarity characteristics to mount cryptanalytic attacks to obtain original images without any knowledge of the encryption/decryption keys. These encryption schemes encrypting the specified region-of-interest (ROI) are also analysed to decrypt ROI encrypted images. Method: The methodology of decryption is key independent and based on divide-and-conquer strategy to obtain original images from given encrypted images. It utilizes the neighbourhood similarity of pixels in an image which is measured in terms of pixel-to-pixel difference between adjacent pixels for pixel inversion based image cipher (GIE) and line-to-line correlation between adjacent lines for pixel rotation based image cipher (CIE). The ROI encrypted and masked encrypted images are also decrypted. Results: Experimental test results show that the decrypted images obtained are quite intelligible and one can understand the contents of decrypted images. It is also seen that an image cipher encrypting the ROI can be decrypted by utilizing unencrypted region surrounding encrypted ROI part of an image. Conclusion: It has been shown that CIE, GIE, ROI and masked encryption schemes reported for image security applications are insecure and not providing adequate security. Such encrypted images can be decrypted without key knowledge successfully with quite intelligibility by considering image similarity characteristics of neighbouring pixels and applying divide-and-conquer attack strategy. Future work: The presented key independent decryption methodology can be considered to cryptanalyze the encryption schemes under noise attack scenario as future work to see the applicability of decryption methods with respect to increase the noise in encrypted images. Moreover, other modern encryption schemes based on pixel inversion and rotation functions can be analysed for their security strength.

Optimizing the quantum circuit for implementing Advanced Encryption Standard (AES) is crucial for estimating the necessary resources in attacking AES by the Grover algorithm. Previous studies have reduced the number of qubits required for the quantum circuits of AES-128/-192/-256 from 984/1112/1336 to 270/334/398, which is close to the optimal value of 256/320/384. It becomes a challenging task to further optimize them. AimTaking aim at this task, we find a method for how the quantum circuit of AES S-box can be designed with the help of the automation tool LIGHTER-R. Particularly, the multiplicative inversion in F28, which is the main part of the S-box, is converted into the multiplicative inversion (and multiplication) in F24, then the latter can be implemented by LIGHTER-R because its search space is small enough. By this method, we construct the quantum circuits of S-box for mapping |a⟩|0⟩ to |a⟩|S(a)⟩ and |a⟩|b⟩ to |a⟩|b ⊕ S(a)⟩ with 20 qubits instead of 22 in the previous studies. In addition, we introduce new techniques to reduce the number of qubits required by the S-box circuit for mapping |a⟩ to |S(a)⟩ from 22 in the previous studies to 16. Accordingly, we synthesize the quantum circuits of AES-128/-192/-256 with 264/328/392 qubits, which implies a new record.

A way to increase the robustness of a cryptographic algorithm toward unauthorized inversion can be obtained through application of non-commutative or non-associative algebraic structures. In this regard, data security became a great issue in adaptation of cloud computing over Internet. While in the traditional encryption methods, security to data in storage state and transmission state is provided, in cloud data processing state, decryption of data is assumed, data being available to cloud provider. In this paper, we propose a special homomorphism between self-distributed and non-associative algebraic structures, which can stand as a premise to construct a homomorphic encryption algorithm aimed at the cloud data security in processing state. Homomorphic encryption so developed will allow users to operate encrypted data directly bypassing the decryption.

M.TECH
Pseudorandom binary sequences find their application in diverse fields but security and cryptography is probably the best known field of their application. One-Time Pad (OTP) is a simple, fast and the most secure encryption algorithm. It provides the perfect secrecy. The encryptiondecryption process of the OTP is based on exclusive-or function computed on the plaintext/ciphertext and the key bits. The requirements for the OTP key are that: it must be a cryptographically strong truly random or pseudorandom binary sequence; must be as long as plaintext size; and must not be reused. The difference between a truly random and a pseudorandom sequence is that the truly random sequence is generated with the help of nondeterministic physical phenomenon but the pseudorandom sequence is generated from some deterministic mechanism and a seed value. In case of pseudorandom binary sequences, given the same seed the pseudorandom number generator will always output the same sequence of numbers or bits. The fundamental difficulty with a truly random sequence is its generation and distribution. Therefore pseudorandom sequences are a popular choice for the practical implementation of the OTP scheme. Many researchers have devoted their time and effort to the family of shift register based pseudorandom sequence generators. But they could not gain a key sequence having very large period equal to the plaintext length. They also tried the complex versions of shift registers but it is yet not very useful and secure