Video encryption is a suitable method to protect video data. In this paper
the existed MPEG video encryption algorithms are classified into four types according to the relationship between encryption process and compression process. They are complete encryption algorithm
partial encryption algorithm
DCT coefficient encryption algorithm and entropy encoding encryption algorithm. Each of them is evaluated from the four aspects: security
compression ratio
computing complexity and operationality. Theoretical analyses and experimental results are presented to compare these algorithms. And their application fields are given
which are consistent with their properties. According to the development direction of video application
the encryption algorithms combining with encoding process will be studied deeply in the future
such as DCT coefficient encryption algorithm
entropy encoding encryption algorithm or novel algorithm combining with error correcting code and so on.