An Image Encryption Algorithm Based on Hyperchaotic System and Variable-Step Josephus Problem

Table 8

The correlation coefficients of the images in different directions.

Images	Correlation
	Original image			Encrypted image
	Horizontal	Vertical	Diagonal	Horizontal	Vertical	Diagonal
Cameraman 128128	0.9530	0.9084	0.8812	−0.0162	0.0015	0.0053
Cameraman 256256	0.9573	0.9134	0.9066	−0.0046	0.0011	0.0159
Cameraman 512512	0.9906	0.9799	0.9710	0.0082	0.0019	0.0088
Brain 128128	0.9829	0.9772	0.9637	−0.0049	0.0004	−0.0057
Brain 256256	0.9857	0.9832	0.9779	−0.0095	−0.0035	−0.0002
Brain 512512	0.9969	0.9961	0.9934	−0.0046	0.0073	0.0063
White 128128	—	—	—	0.0002	0.0043	−0.0002
White 256256	—	—	—	0.0164	−0.0011	0.0003
White 512512	—	—	—	0.0055	0.0037	0.0056
Black 256256	—	—	—	0.0112	−0.0027	0.0040