Plaintext-aware encryption

About: Plaintext-aware encryption is a research topic. Over the lifetime, 1980 publications have been published within this topic receiving 101775 citations. The topic is also known as: Plaintext awareness.

Is the data encryption standard a group

Abstract: The Data Encryption Standard (DES) defines an indexed set of permutations acting on the message space M = {0, l}64. If this set of permutations were closed under functional composition, then DES would be vulnerable to a known-plaintext attack that runs in 228 steps, on the average. It is unknown in the open literature whether or not DES has this weakness.We describe two statistical tests for determining if an indexed set of permutations acting on a finite message space forms a group under functional composition. The first test is a "meet-in-the-middle" algorithm which uses O[?K) time and space, where K is the size of the key space. The second test, a novel cycling algorithm, uses the same amount of time but only a small constant amount of space. Each test yields a known-plaintext attack against any finite, deterministic cryptosystem that generates a small group.The cycling test takes a pseudo-random walk in the message space until a cycle is detected. For each step of the pseudo-random walk, the previous ciphertext is encrypted under a key chosen by a pseudo-random function of the previous ciphertext. Results of the test are asymmetrical: long cycles are overwhelming evidence that the set of permutations is not a group; short cycles are strong evidence that the set of permutations has a structure different from that expected from a set of randomly chosen permutations.Using a combination of software and special-purpose hardware, we applied the cycling test to DES. Our experiments show, with a high degree of confidence, that DES is not a group.

Encryption Performance Improvements of the Paillier Cryptosystem.

Abstract: Homomorphic encryption methods provide a way to outsource computations to the cloud while protecting the confidentiality of the data. In order to deal with the large and growing data sets that are being processed nowadays, good encryption performance is an important step for practicality of homomorphic encryption methods. In this article, we study the encryption performance of the Paillier cryptosystem, a partially homomorphic cryptosystem that allows to perform sums on encrypted data without having to decrypt first. With a combination of both new and known methods, we increase the encryption performance by orders of magnitude compared to a naive implementation. The new methods reduce the bottleneck of noise calculation by using pre-computed noise to generate new noise in a much faster way than by using standard methods.

Image encryption using high-dimension chaotic system

Abstract: In recent years, the chaos based cryptographic algorithms have suggested some new and efficient ways to develop secure image encryption techniques. This paper proposes a new approach for image encryption based on a high-dimensional chaotic map. The new scheme employs the Cat map to shuffle the positions, then to confuse the relationship between the cipher-image and the plain-image using the high-dimensional Lorenz chaotic map preprocessed. The results of experimental, statistical analysis and key space analysis show that the proposed image encryption scheme provides an efficient and secure way for real-time image encryption and transmission.

A chaos-based image encryption algorithm using alternate structure

Abstract: Combined with two chaotic maps, a novel alternate structure is applied to image cryptosystem. In proposed algorithm, a general cat-map is used for permutation and diffusion, as well as the OCML (one-way coupled map lattice), which is applied for substitution. These two methods are operated alternately in every round of encryption process, where two subkeys employed in different chaotic maps are generated through the masterkey spreading. Decryption has the same structure with the encryption algorithm, but the masterkey in each round should be reversely ordered in decryption. The cryptanalysis shows that the proposed algorithm bears good immunities to many forms of attacks. Moreover, the algorithm features high execution speed and compact program, which is suitable for various software and hardware applications.

An efficient image homomorphic encryption scheme with small ciphertext expansion

Abstract: The field of image processing in the encrypted domain has been given increasing attention for the extensive potential applications, for example, providing efficient and secure solutions for privacy-preserving applications in untrusted environment. One obstacle to the widespread use of these techniques is the ciphertext expansion of high orders of magnitude caused by the existing homomorphic encryptions. In this paper, we provide a way to tackle this issue for image processing in the encrypted domain. By using characteristics of image format, we develop an image encryption scheme to limit ciphertext expansion while preserving the homomorphic property. The proposed encryption scheme first encrypts image pixels with an existing probabilistic homomorphic cryptosystem, and then compresses the whole encrypted image in order to save storage space. Our scheme has a much smaller ciphertext expansion factor compared with the element-wise encryption scheme, while preserving the homomorphic property. It is not necessary to require additional interactive protocols when applying secure signal processing tools to the compressed encrypted image. We present a fast algorithm for the encryption and the compression of the proposed image encryption scheme, which speeds up the computation and makes our scheme much more efficient. The analysis on the security, ciphertext expansion ratio, and computational complexity are also conducted. Our experiments demonstrate the validity of the proposed algorithms. The proposed scheme is suitable to be employed as an image encryption method for the applications in secure image processing.