JPEG encryption for image rescaling in the encrypted domain

The JPEG encryption protocol is suitable for image rescaling in encrypted domain.Privacy of the original image can be preserved when transmitted to the server.The encrypted JPEG image can be rescaled by the service provider.On the recipient side, the rescaled image can be decrypted with good quality. This work proposes a novel protocol of encrypting the JPEG image suitable for image rescaling in the encrypted domain. To protect the privacy of original content, the image owner perturbs the texture and randomizes the structure of the JPEG image by enciphering the quantized Discrete Cosine Transform (DCT) coefficients. After receiving the encrypted JPEG image, the service provider generates a rescaled JPEG image by down-sampling the encrypted DCT coefficients. On the recipient side, the encrypted JPEG image rescaled by the service provider can be decrypted to a plaintext image with a lower resolution with the aid of encryption keys. Experimental results show that the proposed method has a good capability of rescaling the privacy-protected JPEG file.