Partial encryption of compressed images and videos

The increased popularity of multimedia applications places a great demand on eecient data storage and transmission techniques. Network communication, especially over a wireless network , can easily be intercepted and must be protected from eavesdroppers. Unfortunately, en-cryption and decryption are slow and it is often diicult, if not impossible, to carry out real-time secure image and video communication and processing. Methods have been proposed to combine compression and encryption together to reduce the overall processing time 3, 4, 12, 18, 20], but they are either insecure or too computationally intensive. We propose a novel solution, called partial encryption, in which a secure encryption algorithm is used to encrypt only part of the compressed data. Partial encryption is applied to several image and video compression algorithms in this paper. Only 13%{27% of the output from quadtree compression algorithms 13, 17, 29, 30, 31, 32] is encrypted for typical images, and less than 2% is encrypted for 512 512 images compressed by the SPIHT algorithm 26]. The results are similar for video compression, resulting in a signiicant reduction in encryption and decryption time. The proposed partial encryption schemes are fast, secure, and do not reduce the compression performance of the underlying compression algorithm.