Recently, image encryption has been significantly improved by methods originating from optics. Phase retrieval is one method potentially applicable to image encryption. It is the process of algorithmically finding solutions to a phase loss problem due to light detectors only capturing the intensity of lights. Because the phase retrieval can constrain information to the phase with a specified condition, we propose using it to encrypt an image and compress it as phase information simultaneously. Moreover, the encryption will involve a customized key known only to authorized users. The encryption strategy provides dual protection of the encrypted image from unauthorized access. Experiments have been conducted to demonstrate the performance of the encryption method.