An Encryption-then-Compression System for Lossless Image Compression Standards

Abstract

SUMMARYIn many multimedia applications, image encryption has to be conducted prior to image compression. This letter proposes an Encryption-then-Compression system using JPEG XR/JPEG-LS friendly perceptual encryption method, which enables to be conducted prior to the JPEG XR/JPEG-LS standard used as an international standard lossless compression method. The proposed encryption scheme can provides approximately the same compression performance as that of the lossless compression without any encryption. It is also shown that the proposed system consists of four block-based encryption steps, and provides a reasonably high level of security. Existing conventional encryption methods have not been designed for international lossless compression standards, but for the first time this letter focuses on applying the standards.

On the Security of Block Scrambling-Based EtC Systems against Extended Jigsaw Puzzle Solver Attacks

“…Block scrambling-based image encryption schemes have been proposed for EtC systems [5]- [8], in which a user wants to securely transmit image I to an audience, via a Social Networking Service (SNS) provider, as illustrated in Fig. 1.…”

“…In the schemes [4]- [8], an image with X × Y pixels is first divided into non-overlapped blocks with B x × B y , then four block scrambling-based processing steps, as illustrated in Fig. 2, is applied to the divided image.…”

“…EtC systems allow us to close unencrypted images to network providers, because encrypted images can be directly compressed even when the images are multiply recompressed by providers. Therefore, we focus on block scrambling-based image encryption schemes, which have been proposed for EtC systems with the assumption of international compression standards, to consider the safety [4]- [8]. So far, the safety has been evaluated based on its key space assuming the brute-force attacks, so that the schemes have enough key spaces for protecting the attacks.…”

Integrated Model of Image Protection Techniques

“…Block-Permutation-Based Encryption (BPBE) schemes [10][11][12][13] comprise one of the perceptual encryption techniques. In BPBE schemes, first, an original image is divided into definite block size, and the four processes of encryption, namely block scrambling, block rotation/inversion, negative-positive transformation and color component shuffling, are processed.…”

“…In BPBE schemes, first, an original image is divided into definite block size, and the four processes of encryption, namely block scrambling, block rotation/inversion, negative-positive transformation and color component shuffling, are processed. The main feature of BPBE schemes is that the compression efficiency of the encrypted images is compatible with JPEG compression [11]. Similarly, the BPBE schemes have been proposed for encryption-then-compression (ETC) technique [14][15][16][17][18][19][20], in which a user securely transmits images via a Social Network Service (SNS) provider.…”