Security-enhanced optical nonlinear cryptosystem based on double random phase encoding

Security is the critical requirement for optical encryption. A security-enhanced nonlinear cryptosystem is designed by introducing a time-varying nonlinear term in the double random phase encoding (DRPE) system. The nonlinear term, which is a randomly generated complex distribution, is introduced in the encryption process and has no influence on the decryption of original image. The nonlinear term is not transmitted to receivers of ciphertexts, therefore, there is no need to manage and distribute it. The designed cryptosystem is demonstrated to be resistant to various attacks including ciphertext-only attacks, known-plaintext attacks and chosen-plaintext attacks. In addition, the nonlinear cryptosystem is simple, and has the same optical implementation as that of conventional DRPE system.