In this paper, a double image encryption mechanism for iris template protection using 3D Lorenz chaotic system with modified equal modulus decomposition in the hybrid transform domain is proposed. The hybrid transform is produced by the combination of Walsh transform, Kekre transform and fractional Fourier transform of various orders. Here the fractional orders of the fractional Fourier transform enlarge the key-space of the proposed scheme and improve robustness against brute-force attack. The proposed scheme is asymmetric and non-linear in nature. To validate and authenticate the proposed cryptosystem, the numerical simulations have been performed on grayscale images. Results demonstrate that the proposed cryptosystem has higher robustness against noise and special attacks.