Length-preserving bit-stream-based JPEG encryption

Abstract

We propose a new method to encrypt baseline JPEG bit streams by selective Huffman code word swapping and coefficient value scrambling based on AES encryption. Furthermore, we show that our approach preserves the length of the bit stream while being completely format-compliant. In contrast to most existing approaches, no recompression is necessary as the encryption is applied directly to the bit stream. In addition, we assess the effort required for brute-force and known-plaintext attacks on pictures encrypted with our approach, showing that both are practically infeasible.