A new encryption/decryption system is designed for information security. The system used an iterative Fourier transform algorithm to optimize the encrypted hologram as well as the decryption key as phase-only elements. The optical decryption was implemented by superimposing the encrypted hologram and the decryption key in a simple optical setup, Numerical simulation and optical experiment have confirmed the proposed technique as a simple and easy implementation for optical decryption,demonstrating potential applications in information security verification. This system provides an advantage to encode information in an invisible element. Computer simulations have demonstrated the effectiveness of this technique.