A Perceptually Scalable and JPEG Compression Tolerant Image Encryption Scheme

In this paper, a perceptually scalable and JPEG compression tolerant DCT-based image encryption scheme is proposed. There are two main features of the proposed scheme, first the decryption algorithm is able to reconstruct the plaintext-image even if the encrypted image is JPEG compressed. Secondly, the encryption algorithm can be adjusted to produce cipher-image with varying perceptual distortion. The proposed encryption scheme relies on some very interesting properties of orthogonal matrices containing columns that form a set of orthonormal basis vectors. It is envisaged that the proposed cryptosystem would enable uncompressed encrypted image files to be transmitted or stored in the JPEG compressed domain thus saving bandwidth and or storage space. Further, the proposed scheme can be used either for low-level encryption in which the cipher-image has a degraded visual quality but reflects the contents of the plaintext-image, or high-level encryption in which the cipher-image does not reveal any information about the plaintext-image. Experimental results and security analysis is presented to show the viability of the proposed scheme.