Cryptanalysis of an image encryption scheme based on the Hill cipher

This paper studies the security of an image encryption scheme based on the Hill cipher (Ismail et al., 2006) and reports its following problems: (1) There is a simple necessary and sufficient condition that makes a number of secret keys invalid; (2) It is insensitive to the change of the secret key; (3) It is insensitive to the change of the plain-image; (4) It can be broken with only one known/chosen plaintext; (5) It has some other minor defects. The proposed cryptanalysis discourages any use of the scheme in practice.

Lossless embedding: A visually meaningful image encryption algorithm based on hyperchaos and compressive sensing

A novel visually meaningful image encryption algorithm is proposed based on a hyperchaotic system and compressive sensing(CS), which aims to improve the visual security of steganographic image and decrypted quality. First, a dynamic spiral block scrambling is designed to encrypt the sparse matrix generated by performing discrete wavelet transform(DWT)on the plain image. Then, the encrypted image is compressed and quantified to obtain the noise-like cipher image. Then the cipher image is embedded into the alpha channel of the carrier image in portable network graphics(PNG) format to generate the visually meaningful steganographic image. In our scheme, the hyperchaotic Lorenz system controlled by the hash value of plain image is utilized to construct the scrambling matrix, the measurement matrix and the embedding matrix to achieve higher security. In addition, compared with other existing encryption algorithms, the proposed PNG-based embedding method can blindly extract the cipher image, thus effectively reducing the transmission cost and storage space. Finally, the experimental results indicate that the proposed encryption algorithm has very high visual security.

Non-Associative Algebra Redesigning Block Cipher with Color Image Encryption

The substitution box(S-box)is a fundamentally important component of symmetric key cryptosystem.An S-box is a primary source of non-linearity in modern block ciphers,and it resists the linear attack.Various approaches have been adopted to construct S-boxes.S-boxes are commonly constructed over commutative and associative algebraic structures including Galois fields,unitary commutative rings and cyclic and non-cyclic finite groups.In this paper,first a non-associative ring of order 512 is obtained by using computational techniques,and then by this ring a triplet of 8×8 S-boxes is designed.The motivation behind the designing of these S-boxes is to upsurge the robustness and broaden the key space due to non-associative and noncommutative behavior of the algebraic structure under consideration.A novel color image encryption application is anticipated in which initially these 3 S-boxes are being used to produce confusion in three layers of a standard RGB image.However,for the sake of diffusion 3D Arnold chaotic map is used in the proposed encryption scheme.A comparison with some of existing chaos and S-box dependent color image encryption schemes specs the performance results of the anticipated RGB image encryption and observed as approaching the standard prime level.

A fast image encryption algorithm based on only blocks in cipher text

In this paper, a fast image encryption algorithm is proposed, in which the shuffling and diffusion is performed simul- taneously. The cipher-text image is divided into blocks and each block has k x k pixels, while the pixels of the plain-text are scanned one by one. Four logistic maps are used to generate the encryption key stream and the new place in the cipher image of plain image pixels, including the row and column of the block which the pixel belongs to and the place where the pixel would be placed in the block. After encrypting each pixel, the initial conditions of logistic maps would be changed ac- cording to the encrypted pixel＇s value; after encrypting each row of plain image, the initial condition would also be changed by the skew tent map. At last, it is illustrated that this algorithm has a faster speed, big key space, and better properties in withstanding differential attacks, statistical analysis, known plaintext, and chosen plaintext attacks.

How to repair the Hill cipher

The Hill cipher algorithm is one of the symmetric key algorithms that have several advantages in data encryption. However, a main drawback of this algorithm is that it encrypts identical plaintext blocks to identical ciphertext blocks and cannot encrypt images that contain large areas of a single color. Thus, it does not hide all features of the image which reveals patterns in the plaintext. Moreover, it can be easily broken with a known plaintext attack revealing weak security. This paper presents a variant of the Hill cipher that overcomes these disadvantages. The proposed technique adjusts the encryption key to form a dif- ferent key for each block encryption. Visually and computationally, experimental results demonstrate that the proposed variant yields higher security and significantly superior encryption quality compared to the original one.

Comment:Comments on “How to repair the Hill cipher”

A modification of the Hill cipher algorithm was recently proposed by Ismail et al.(2006),who claimed that their new scheme could offer more security than the original one due to an extra non-linearity layer introduced via an elaborated key gen-eration mechanism.That mechanism produces one different encryption key for each one of the plaintext blocks.Nevertheless,we show in this paper that their method still has severe security flaws whose weaknesses are essentially the same as that already found in the original Hill cipher scheme.

An Efficient Technique to Prevent Data Misuse with Matrix Cipher Encryption Algorithms

Many symmetric and asymmetric encryption algorithms have been developed in cloud computing to transmit data in a secure form.Cloud cryptography is a data encryption mechanism that consists of different steps and prevents the attacker from misusing the data.This paper has developed an efficient algorithm to protect the data from invaders and secure the data from misuse.If this algorithm is applied to the cloud network,the attacker will not be able to access the data.To encrypt the data,the values of the bytes have been obtained by converting the plain text to ASCII.A key has been generated using the Non-Deterministic Bit Generator(NRBG)mechanism,and the key is XNORed with plain text bits,and then Bit toggling has been implemented.After that,an efficient matrix cipher encryption algorithm has been developed,and this algorithm has been applied to this text.The capability of this algorithm is that with its help,a key has been obtained from the plain text,and only by using this key can the data be decrypted in the first steps.A plain text key will never be used for another plain text.The data has been secured by implementing different mechanisms in both stages,and after that,a ciphertext has been obtained.At the end of the article,the latest technique will be compared with different techniques.There will be a discussion on how the present technique is better than all the other techniques;then,the conclusion will be drawn based on comparative analysis.

An Efficient Image Cipher Based on 2D Scrambled Image and Random Numbers

Security of images plays an import role in communication in current era due to the popularity and high usage ofmultimedia content in the Internet.Image security is described as applying an encryption algorithm over the given plaintext images to produce cipher images that can be transmitted safely over the open channel,the Internet.The problem which plagues these image ciphers is that they are too much time consuming,and that do not meet the dictates of the present times.In this paper,we aim to provide an efficient image cipher.The previous studies employed many constructs like Langton’s Ant,15 puzzle game and Castle in the 2D scrambled image based image ciphers,which had grave implications related to the high execution time of the ciphers.The current study directly made use of the 2D scrambled image to realize the purpose.Moreover,no compromise has been made over the security of the proposed image cipher.Random numbers have been generated by triggering the Intertwining Logistic Chaotic map.The cipher has been subjected to many important validation metrics like key space,information entropy,correlation coefficient,crop attack and lastly time complexity to demonstrate its immunity to the various attacks,and its realworld application.In this paper,our proposed image cipher exhibits an encryption speed of 0.1797 s,which is far better than many of the existing encryption ciphers.

Hill Matrix and Radix-64 Bit Algorithm to Preserve Data Confidentiality

There are many cloud data security techniques and algorithms available that can be used to detect attacks on cloud data,but these techniques and algorithms cannot be used to protect data from an attacker.Cloud cryptography is the best way to transmit data in a secure and reliable format.Various researchers have developed various mechanisms to transfer data securely,which can convert data from readable to unreadable,but these algorithms are not sufficient to provide complete data security.Each algorithm has some data security issues.If some effective data protection techniques are used,the attacker will not be able to decipher the encrypted data,and even if the attacker tries to tamper with the data,the attacker will not have access to the original data.In this paper,various data security techniques are developed,which can be used to protect the data from attackers completely.First,a customized American Standard Code for Information Interchange(ASCII)table is developed.The value of each Index is defined in a customized ASCII table.When an attacker tries to decrypt the data,the attacker always tries to apply the predefined ASCII table on the Ciphertext,which in a way,can be helpful for the attacker to decrypt the data.After that,a radix 64-bit encryption mechanism is used,with the help of which the number of cipher data is doubled from the original data.When the number of cipher values is double the original data,the attacker tries to decrypt each value.Instead of getting the original data,the attacker gets such data that has no relation to the original data.After that,a Hill Matrix algorithm is created,with the help of which a key is generated that is used in the exact plain text for which it is created,and this Key cannot be used in any other plain text.The boundaries of each Hill text work up to that text.The techniques used in this paper are compared with those used in various papers and discussed that how far the current algorithm is better than all other algorithms.Then,the Kasiski test is used to verify the validity of the proposed algorithm and found that,if the proposed algorithm is used for data encryption,so an attacker cannot break the proposed algorithm security using any technique or algorithm.

Two Layer Symmetric Cryptography Algorithm for Protecting Data from Attacks

Many organizations have insisted on protecting the cloud server from the outside,although the risks of attacking the cloud server are mostly from the inside.There are many algorithms designed to protect the cloud server from attacks that have been able to protect the cloud server attacks.Still,the attackers have designed even better mechanisms to break these security algorithms.Cloud cryptography is the best data protection algorithm that exchanges data between authentic users.In this article,one symmetric cryptography algorithm will be designed to secure cloud server data,used to send and receive cloud server data securely.A double encryption algorithm will be implemented to send data in a secure format.First,the XOR function will be applied to plain text,and then salt technique will be used.Finally,a reversing mechanism will be implemented on that data to provide more data security.To decrypt data,the cipher text will be reversed,salt will be removed,andXORwill be implemented.At the end of the paper,the proposed algorithm will be compared with other algorithms,and it will conclude how much better the existing algorithm is than other algorithms.

Split-n-Swap: A New Modification of the Twofish Block Cipher Algorithm

Securing digital data from unauthorized access throughout its entire lifecycle has been always a critical concern.A robust data security system should protect the information assets of any organization against cybercriminal activities.The Twofish algorithm is one of the well-known symmetric key block cipher cryptographic algorithms and has been known for its rapid convergence.But when it comes to security,it is not the preferred cryptographic algorithm to use compared to other algorithms that have shown better security.Many applications and social platforms have adopted other symmetric key block cipher cryptographic algorithms such as the Advanced Encryption Standard(AES)algorithm to construct their main security wall.In this paper,a new modification for the original Twofish algorithm is proposed to strengthen its security and to take advantage of its fast convergence.The new algorithm has been named Split-n-Swap(SnS).Performance analysis of the new modification algorithm has been performed using different measurement metrics.The experimental results show that the complexity of the SnS algorithm exceeds that of the original Twofish algorithm while maintaining reasonable values for encryption and decryption times as well as memory utilization.A detailed analysis is given with the strength and limitation aspects of the proposed algorithm.

用MATLAB实现HILL密码的加密与解密

在当今的通讯领域,信息的安全性非常重要,因此常常需要对信息进行加密和解密。作为以代数为基础的密码学,HILL密码具有一定的实用价值。依照HILL密码的原理,借助MATLAB,准确快速地实现HILL密码的加密和解密。

Hill密码加密解密时矩阵的求法

在计算机网络中,为了保证数据的安全,常常要对数据进行加密和解密。文章运用数学知识和Matlab语言,介绍了Hill密码加密时如何给出密钥矩阵以及解密时如何求密钥矩阵的逆,从而实现Hill密码快速加密和解密。

用逆向思维求Hill密码加密解密时的矩阵

在计算机网络中,为了保证数据的安全,常常要对数据进行加密和解密。运用数学知识和MATLAB语言,介绍了Hill密码加密时如何给出密钥矩阵以及解密时如何求密钥矩阵的逆,从而实现Hill密码快速加密和解密。

一种基于Hill密码思想的数据库密码编码算法

由于数据库系统仅支持ASCII字符集中的可打印字符,将加密后的记录编码成可打印字符是保证数据库系统正常运行的关键,文中将这一过程称作密文编码。许多现有算法不能将对记录的加密和编码过程结合起来,在时间效率或安全性上存在不足。本文提出一种基于Hill密码思想的数据库密文编码算法,该算法将对记录的加密和加密后的编码合为一个过程,可以很好地解决数据库记录加密和编码问题。它实际上是一种对数据库记录的双重保护机制,具有比同类算法更高的安全性和时间效率。文中还分析了该算法的时间复杂性和安全性,最后提出了下一步的研究方向和目标。

Construction of a key-dependent message secure symmetric encryption scheme in the ideal cipher model

Key-dependent message （KDM） security is an important security issue that has attracted much research in recent years. In this paper, we present a new construction of the symmetric encryption scheme in the the ideal cipher model （ICM）; we prove that our scheme is KDM secure against active attacks with respect to arbitrary polynomialtime challenge functions. Our main idea is to introduce a universal hash function （UHF） h as a random value for each encrypfion, and then use s = h（sk） as the key of the ideal cipher F, where sk is the private key of our symmetric encryption scheme. Although many other schemes that are secure against KDM attacks have already been proposed, in both the ideal standard models, the much more significance of our paper is the simplicity in which we implement KDM security against active attacks.

Secure and Robust Optical Multi-Stage Medical Image Cryptosystem

Due to the rapid growth of telemedicine and healthcare services,color medical image security applications have been expanded precipitously.In this paper,an asymmetric PTFrFT(Phase Truncated Fractional Fourier Transform)-based color medical image cryptosystem is suggested.Two different phases in the fractional Fourier and output planes are provided as deciphering keys.Accordingly,the ciphering keys will not be employed for the deciphering procedure.Thus,the introduced PTFrFT algorithm comprises asymmetric ciphering and deciphering processes in contrast to the traditional optical symmetric OSH(Optical Scanning Holography)and DRPE(Double Random Phase Encoding)algorithms.One of the principal impacts of the introduced asymmetric cryptosystem is that it eliminates the onedimensionality aspects of the related symmetric cryptosystems due to its remarkable feature of phase nonlinear truncation components.More comparisons on various colormedical images are examined and analyzed to substantiate the cryptosystem efficacy.The achieved experimental outcomes ensure that the introduced cryptosystem is robust and secure.It has terrific cryptography performance compared to conventional cryptography algorithms,even in the presence of noise and severe channel attacks.

基于密码反馈秘密共享的大容量密文域可逆隐藏

为提高分布式环境下密文域可逆信息隐藏算法的安全性、鲁棒性和嵌入率,提出了一种基于密码反馈秘密共享的多重嵌入算法。首先,利用秘密共享加密过程中产生的多项式冗余系数进行嵌入;其次,利用秘密共享的同态加性对秘密份额二次嵌入。实验结果表明,所提算法利用反馈机制提高了秘密共享的扩散特性从而增强了算法安全性和鲁棒性,在(3,4)和(3,5)门限下,嵌入率分别为6.00 bpp和4.80 bpp。所提算法具有安全性高、完全可逆、嵌入率较大等特点;算法嵌入率不受载体图像影响,仅与算法参数选择有关。

基于双域联合编码和秘密共享的密文域可逆信息隐藏

针对如何提高可逆信息隐藏算法的安全性和嵌入容量的问题,提出了一种基于双域联合编码和密码反馈秘密共享的密文域可逆信息隐藏算法。首先,对图像进行中值边缘检测器(median-edge detector,MED)预测,计算最优水平l,并将像素分成可预测像素和不可预测像素;其次,使用双域联合编码分别在像素域和比特域上压缩辅助信息,以便提供更多的可嵌入空间;再次,使用密码反馈秘密共享技术将原始图像加密生成多个加密图像,并将辅助信息和多方的秘密数据嵌入到多个加密图像中;最后,根据提取的辅助信息,100%恢复秘密数据以及原始图像。实验结果表明,该算法显著提高了嵌入容量和安全性。

基于新余弦混沌映射的视觉安全图像加密算法

考虑到目前图像加密算法缺少了对加密后图像的视觉安全的保护,将新余弦混沌映射和贝叶斯压缩感知进行结合提出一种视觉有意义的图像加密算法是非常有价值的.首先,基于余弦函数提出了一个新的一维混沌映射用于构建受控测量矩阵,除此之外,所提出的新余弦混沌映射能够更好地扰乱图像的强相关性.其次,通过二维Arnold置乱算法对明文图像的小波包系数矩阵进行置乱.然后,借助混沌测量矩阵和双向加模扩散策略对置乱后的秘密图像进行压缩和加密.最后,通过最低有效位嵌入算法将秘密图像嵌入到经过生命游戏混合置乱后的载体图像中以得到一幅具有视觉意义的密文图像.仿真结果和安全性分析表明在保证视觉安全性和解密质量的前提下所提加密算法具备可行性和高效性.