Encrypted JPEG image retrieval using histograms of transformed coefficients

This work proposes an encrypted JPEG image retrieval mechanism based on the histograms of transformed coefficients. With this scheme, JPEG image is encrypted during its compression process by using other orthogonal transforms for blocks' transformation, rather than 8×8 DCT. Then the encrypted images are transferred to and stored in the cloud server. When receiving an encrypted query image from the authorized user, the server calculates the histograms of transformed coefficients located at different frequency positions. By computing the distance between the histograms of encrypted query image and database cipherimages, encrypted images with plaintext content similar to the query image are retured to the authorized user for decryption. Experiments are conducted to show that our scheme can provide effective cipherimage retrieval service, while ensure format compliance and compression friendly.