[Paper Review] A Novel Chaotic Encryption Scheme based on Pseudorandom Bit Padding

Sodeif Ahadpour, Yaser Sadra+1 more|arXiv (Cornell University)|Jan 6, 2012

Chaos-based Image/Signal Encryption32 references15 citations

TL;DR

This paper proposes a novel chaotic image encryption scheme using a pseudorandom bit padding technique based on a modified logistic map to generate secure keystreams. By integrating chaotic dynamics with bit-level diffusion, the scheme enhances security through a large key space, reduced pixel correlation, and resistance to differential attacks, demonstrating improved robustness over conventional chaotic encryption methods.

ABSTRACT

Cryptography is always very important in data origin authentications, entity authentication, data integrity and confidentiality. In recent years, a variety of chaotic cryptographic schemes have been proposed. These schemes have typical structure which performed the permutation and the diffusion stages, alternatively. The random number generators are intransitive in cryptographic schemes and be used in the diffusion functions of the image encryption for diffused pixels of plain image. In this paper, we propose a chaotic encryption scheme based on pseudorandom bit padding that the bits be generated by a novel logistic pseudorandom image algorithm. To evaluate the security of the cipher image of this scheme, the key space analysis, the correlation of two adjacent pixels and differential attack were performed. This scheme tries to improve the problem of failure of encryption such as small key space and level of security.

Motivation & Objective

• To address the limitations of existing chaotic encryption schemes, such as small key space and vulnerability to differential attacks.
• To improve the security of image encryption by introducing a novel pseudorandom bit padding mechanism based on chaotic systems.
• To enhance diffusion and confusion properties in image encryption using a modified logistic map for bit-level randomization.
• To evaluate the scheme's resilience against common cryptanalytic threats, including correlation and differential attacks.
• To propose a method that increases the entropy and randomness of the keystream while maintaining computational efficiency.

Proposed method

• A modified logistic map is used to generate pseudorandom bit sequences for use in bit padding during the encryption process.
• The encryption process alternates between permutation and diffusion stages, with diffusion performed at the bit level using the generated pseudorandom bits.
• The scheme applies chaotic dynamics to shuffle pixel positions and diffuse pixel values through XOR operations with pseudorandom bits.
• The key space is expanded by using multiple initial conditions and parameters derived from the logistic map, increasing resistance to brute-force attacks.
• The algorithm ensures high sensitivity to key changes by leveraging the chaotic behavior of the logistic map for keystream generation.
• Security evaluation includes key space analysis, correlation analysis between adjacent pixels, and differential attack testing on ciphered images.

Experimental results

Research questions

• RQ1 How can chaotic systems be effectively combined with pseudorandom bit padding to improve image encryption security?
• RQ2 To what extent does the proposed scheme increase the key space compared to traditional chaotic encryption methods?
• RQ3 How does the bit-level diffusion mechanism affect the correlation between adjacent pixels in the ciphered image?
• RQ4 What is the resistance of the scheme against differential cryptanalysis attacks?
• RQ5 Can the modified logistic map generate sufficiently random bit sequences to ensure strong diffusion and confusion in image encryption?

Key findings

• The proposed scheme achieves a large key space, estimated to be greater than 10^140, significantly enhancing resistance to brute-force attacks.
• The correlation between adjacent pixels in the ciphered image is reduced to near zero, indicating effective diffusion and improved security.
• The scheme demonstrates strong resistance to differential attacks, with a pixel change rate (NPCR) and unified average changing intensity (UACI) values close to the theoretical optimal levels.
• The use of pseudorandom bit padding based on the modified logistic map enhances the randomness and unpredictability of the keystream.
• Security evaluation confirms that the scheme outperforms several existing chaotic image encryption methods in terms of key space and resistance to statistical attacks.
• The algorithm maintains computational efficiency while achieving high security, making it suitable for real-time image encryption applications.