In this paper, a novel method for symmetric image encryption using Lorenz chaotic system is proposed. The main operations performed in the proposed system are keystream generation, permutation, and diffusion. In the permutation phase, both pixel-level and bit-level scrambling are performed to achieve the double scrambling property. The pixel-level scrambling is implemented by a novel approach using two different keystreams. Also, the bit-level scrambling is realized with a novel approach using cyclic shift operation and a keystream. Thus, the double scrambling ensures higher security in the permutation process. The images are encrypted by an enhanced diffusion process using another keystream. The permutation and diffusion processes use different keystreams generated from the Lorenz system with chaotic behavior. A novel method is adopted for the keystream generation phase. The security of the proposed cryptosystem has been assessed by various evaluation metrics like sensitivity analysis on key and cipher images, information entropy analysis, occlusion attack, and diverse statistical explorations such as correlation and histogram analyses. The experimental results show the supremacy and better performance of the proposed cryptosystem compared to several state-of-the-art techniques.

本文提出了一种新的基于洛伦兹混沌系统的对称图像加密方法。在所提出的系统中执行的主要操作是密钥流生成、排列和扩散。在置换阶段，同时进行像素级和位级加扰以实现双加扰特性。像素级加扰是通过使用两个不同密钥流的新颖方法实现的。此外，比特级加扰是通过使用循环移位操作和密钥流的新颖方法实现的。因此，双加扰确保了置换过程中更高的安全性。图像通过使用另一个密钥流的增强扩散过程进行加密。置换和扩散过程使用从具有混沌行为的洛伦兹系统生成的不同密钥流。密钥流生成阶段采用了一种新方法。所提出的密码系统的安全性已通过各种评估指标进行评估，例如对密钥和密码图像的敏感性分析、信息熵分析、遮挡攻击以及各种统计探索，例如相关性和直方图分析。实验结果表明，与几种最先进的技术相比，所提出的密码系统具有优越性和更好的性能。