  In recent work, various fractal image coding methods are reported, which
adopt the self-similarity of images to compress the size of images. However,
till now, no solutions for the security of fractal encoded images have been
provided. In this paper, a secure fractal image coding scheme is proposed and
evaluated, which encrypts some of the fractal parameters during fractal
encoding, and thus, produces the encrypted and encoded image. The encrypted
image can only be recovered by the correct key. To keep secure and efficient,
only the suitable parameters are selected and encrypted through in-vestigating
the properties of various fractal parameters, including parameter space,
parameter distribu-tion and parameter sensitivity. The encryption process does
not change the file format, keeps secure in perception, and costs little time
or computational resources. These properties make it suitable for secure image
encoding or transmission.
