Breaking an Image Encryption Scheme Based on Chaotic Synchronization Phenomenon

In recent past, Volos et al. proposed an image encryption scheme based on true random bits generator in [Signal Processing 93, 1328-1340, 2013]. The TRBG uses two mutually coupled double scroll chaotic systems that are synchronized via complete chaotic synchronization and inverse pi-lag synchronization techniques. The numerical simulations demonstrated the effectiveness of chaotic true random bits generator through FIPS-140-2 randomness test suite. The proposed generator is applied with an aim to secure the digital images by framing an image encryption process based on the effective TRBG. The statistical analyses conform to the required encryption standards and quality. But, Volos et al. image encryption scheme inherently holds a number of vulnerabilities that make it possible to break the encryption scheme. This paper proposes the break of the Volos et al. image encryption scheme by exploiting these vulnerabilities to evidence that their scheme lacks security. It is practically shown by applying the chosen-plaintext and known-plaintext attacks which successfully recovers the plaintext-image from the encrypted image without knowing the secret key. The idea is to show the ineligibility of the encryption scheme for use in practical image security applications.