A new simple chaotic system and its application in medical image encryption

Today, medical imaging suffers from serious issues such as malicious tampering and privacy leakage. Encryption is an effective way to protect these images from security threats. Among the available encryption algorithms, chaos-based methods have strong cryptographic properties, because chaotic systems are sensitive to initial conditions and parameters. However, traditional chaotic systems are easy to build, analyze, predict and can be re-scaled to any desired frequency. Thus, encryption schemes using traditional chaotic systems have low security levels. In this work, we propose a new simple chaotic system that utilizes a hyperbolic sine as its nonlinearity; this nonlinearity has rarely appeared in previous studies. Furthermore, the new chaotic system uses a decorrelation operation to enhance its performance. Statistical testing verifies that the chaotic sequence has good pseudorandom characteristics. In this study, we propose a scheme for medical image encryption based on this new chaotic system. The results of tests show that this encryption method can encrypt images effectively in a single round and that the proposed scheme provides sufficient security against known attacks.