A fast image-scramble method using public-key encryption allowing backward compatibility with JPEG2000

A new method for partial-scrambling of JPEG 2000 images based on public-key encryption is proposed. By using public-key encryption, the proposed method provides an easier way of managing the encryption key compared with the secret-key based method and also provides tamper resistance against attacks. Although public-key encryption is usually very time-consuming, the proposed method achieves fast encryption by controlling the number of bytes to be encrypted. An encrypted JPEG 2000 image generated by the proposed method has backward compatibility with a standard JPEG 2000 image, so that it can be decoded using a standard JPEG 2000 decoder. The proposed method also has scalability as to the degree of scrambling on the basis of JPEG 2000 coding units, i.e.. layers. DWT-levels, subbands. or code-blocks.