A novel image encryption technique is proposed. The encrypted image is obtained by randomly changing the phase spectra of the original image. Therefore, the resulting image is unrecognized and the image encryption is achieved. The phase spectra of the original image are added with the binary phase spectra of a pseudo-noise. This type of image encryption is similar to the private-key cryptographic system. The attack study for the proposed image encryption scheme is also conducted. It is shown that the possibility of a successful attack for a 512 × 512 encrypted image is, at most, 1.25 × 10-11 which requires 84 years by the state-of-the-art technology. The application of this type of encryption for the progressive transmission is also conducted. It is found that any part of the encrypted image can be used to reconstruct a meaningful original image. In addition, the encrypted image is insensitive to the presence of data loss. Therefore, in avoiding the network congestion it is suitable for the multimedia communications.