Hybrid Image Encryption

Partial image encryption has several advantages compared to standard encryption in the multimedia domain. It preserves structural information of the media files and allows viewing the files in their encrypted state. The drawbacks of partial encryption are the lower security and the file size increase. We propose hybrid encryption, where the most significant frequency bands are strongly encrypted and the other bands are encrypted in a codingfriendly manner to achieve the best compromise between security and file size. We apply this concept to a local encryption approach where facial parts of photographs are recognized and encrypted to achieve a privacy-preserving state of a photo which can efficiently can be decrypted if required.