Images encryption via Discrete Fractional Fourier Transform and Jigsaw transform. Case study: Fingerprints

A new images encryption method using The Discrete Fractional Fourier Transform (DFrFT) and the Jigsaw transform is proposed. The main feature of this encryption scheme is that the encrypted image is real and has the same size as the original one, being this encrypted image much more convenient for either its storage or its transmission on digital communication networks. Using the Jigsaw transform the security of the encrypted image is increased and the random phase masks used in many images cryptosystems based on Fractional Fourier Transform (FrFT) are eliminated. Finally, for the new proposed encryption method, a fingerprint encryption digital algorithm was developed. There are twelve keys used in the cryptographic algorithm implemented, which are constituted by the six DFrFTs fractional orders and the six random permutations used in Jigsaw transform; all these keys are necessary for a correct decryption, obtaining a high level security in protecting fingerprints for a particular application.