# Hash Based DNA Computing Algorithm for Image Encryption
## 1 Introduction
Inspired by the idea of utilizing DNA computing to encrypt, we aim to encrypt high-dimensional image data in this paper. Compared with text structure data, the image is characterized with high-dimensional and unstructured proposes, which have two major difficulties in designing proper encryption algorithms. **First**, how to achieve an unbreakable capability for image data with less encoding complexity, since a more complex encoding strategy generally promotes encryption performance. **Second**, since the image is equipped with a natural property of high-dimensional complexity, how algorithms could involve such a property for for encoding. In other words, images are a natural source of randomness, where adjacent pixels marked with a considerable amount of redundant information demonstrate strong correlations. Therefore, the characteristic of smooth variation between pixels can be leveraged to speed up the image encryption process. To address the above difficulties, we develop a novel hash encoding-based DNA computing algorithm to effectively encrypt high-dimensional image data, which consists of the DNA hash encoding module and content-aware encrypting module. The hash algorithm is unique in encrypting, which outputs a fixed-length output with data as complicated as possible. Moreover, it shares several impressive characteristics, such as a small computing burden with a simple function calculation; unidirectionality without possible ways to reverse the input data through hash results, tampering resistance where small modification would greatly vary the output results; and anti-collision capability, which guarantees that the unique output could be gained with different inputs. Inspired by these properties, we involve hash encoding into DNA computing inside the proposed DNA hash encoding module, thus boosting the encryption capability of high-dimensional data with a small computation burden. Considering high-dimensional image data as a natural source to encode with less complexity, a content-aware encrypting module is proposed to map between image content and encryption results with several simple but effective functions, thus offering new ways to encrypt images based on DNA computing. To sum up, the contributions of this paper are three-fold:* The proposed method combines the impressive characteristics of DNA computing and the hash function to realize an unbreakable image encryption with less computation burden. * A novel DNA-based hash encoding module is proposed, which involves the hash function to construct mappings from high-dimensional image data to DNA bases. * Considering correlations between adjacent pixels as natural sources of complexity, the proposed content-aware encrypting module sumcesfully generates random DNA sequences with chaos properties, which adopts non-linear functions originating from correlations of pixles as source of complexity. The rest of this paper is organized as follows. Section 2 reviews the related work. Section 3 first presents an overview on algorithm structure, and then presents detailed steps of encryption and decryption. Section 4 conducts several experiments, including an analysis on the key space, histogram, pixel correlation, information entropy, sensitivity and computation cost. Finally, Section 5 concludes the paper and demonstrates the prospect.