Table 6.

Pixel correlation coefficients in three directions: horizontal (H), diagonal (D) and vertical (V) for encrypted images.

Encrypted image	H	D	V
Mandrill	0.00307613	0.000809074	− 0.00521955
Peppers	− 0.00329259	− 0.00567403	0.000306954
F16	0.00046871	− 0.00129673	− 0.0015519
Sailboat	− 0.00579529	0.00357263	0.00601578
Tree	0.00122393	− 0.00043615	− 0.00441973
Apples	− 0.00213933	0.00248506	− 0.010287
Average	− 0.00107641	− 0.00009002	− 0.00025259