Cryptanalysis and Improvement of Chaos-Based Image Encryption Scheme with Circular Inter-Intra-Pixels Bit-Level Permutation

Table 2

NPCR and UACI values of different images by different algorithms.

Image	NPCR (%)
	Ref. [21]	Ref. [22]	Ref. [23]	Original	Improved
Lena	99.61	99.55	99.61	99.62	99.60
Peppers	99.61	99.58	99.62	99.61	99.61
Couple	99.63	99.56	99.63	99.63	99.64
Cameraman	99.63	99.57	99.61	99.60	99.63
Boat	99.63	99.56	99.62	99.61	99.59
Image	UACI (%)
	Ref. [21]	Ref. [22]	Ref. [23]	Original	Improved
Lena	33.56	33.34	33.63	33.48	33.47
Peppers	33.63	33.35	33.74	33.51	33.40
Couple	33.64	33.37	33.72	33.49	33.45
Cameraman	33.71	33.37	33.69	33.52	33.59
Boat	33.61	33.42	33.60	33.49	33.32