In this work we proposed one optical setup for encryption based in the fractional Fourier Transform. The Fourier transform of fractional order add another degree of freedom, of course the degree fractional used, for the optical encryption realization. The inverse fractional Fourier transform is perform by phase conjugation. This technique allows use the optical setup for encryption and decryption simultaneously. Based in experimental results and numerical simulations we find that is not arbitrary the use of the keys for encryption and decryption operations. The optical fractional Fourier transform has been obtained using the Lohmann type I configuration and a photorefractive crystal BGO working as mirror phase conjugation has been used.