An encryption algorithm of JPEG2000 streams for supporting ciphertext-based transcoding

With the increasing demands on image transcoding in heterogeneous networks, a ciphertext-based transcoding hierarchical encryption algorithm (CT-HEA) is proposed for JPEG2000 streams. By utilizing the rate-distortion optimized truncation, CT-HEA rearranges the compressed bitstream according to the quality layer and the resolution of the image, and then applies a hierarchical encryption scheme to the reorganized codestream via using cryptographic functions. This supports transparent transcoding operations directly on the compressed and encrypted bitstream. Simulation results demonstrate that the proposed CT-HEA has high transcoding flexibility with a low transcoding costs.