A time-efficient and noise-resistant cryptosystem based on discrete wavelet transform and chaos theory: An application in image encryption

Abstract

Due to the exponential rise of multimedia technologies, digital information privacy is now more crucial than ever. The process of transmitting data across a channel such as the internet has become a challenging task. In recent years, a variety of techniques for encrypting digital data have been proposed. However, due to shortcomings such as a high computational cost and weak security, it is important to build an encryption scheme that can provide a suitable level of security while also being time-effective. This research introduces a Discrete Wavelet Transform (DWT), chaotic map, and substitution box-based encryption scheme that is both time efficient and provides high levels of security for digital images. DWT is utilized to reduce the computation complexity of the encryption scheme proposed in this research. This is done by transforming the input image into its four frequency sub-bands (ΓΓ, Γħ, ħΓ, and ħħ) and selecting only the low-frequency sub-band (ΓΓ) for encryption, while the substitution boxes (S-boxes) and a chaotic map are used to increase the level of security. Using chaotic maps, random sequences are also generated to introduce confusion and diffusion. The final encrypted image is created by combining all of the non-modified and encrypted frequency bands. Finally, the results show that proposed encryption system nears the optimum values with a key-space of 2265 to avoid a brute-force attack.