Visual cryptography scheme by freeform optics based on optimal mass transport

An information hiding scheme for visual cryptography based on freeform optics is provoked. The encryption and decryption of information are achieved by the redistribution of light energy between two freeform surfaces lenses. Each freeform lens provides a preset light energy distribution constructed by optimal mass transport theory, and the hidden information can be clearly displayed only by illuminating the encryptor with the distribution of the decryptor. The encryption key can be transmitted in the form of freeform lens coordinates on Internet, and the decryption process can be completed by a single computer. The simulation results show that the encrypted information can be clearly showed when using the preset decryptor distribution and decryption conditions. When encryptor is illuminated by other distribution or the decryption conditions do not match, the hidden information cannot be displayed. By increasing the complexity of decryptor distribution, the security of encrypted information can be further strengthened. This visual cryptography scheme admit the daily secret communication because of its good transmission privacy and strong security.