Fig 1.
Sequence trajectories of system (1) with (a1, a2, a3, a4, a5, a6, a7) = (10, 1, 28, 8/3, 2, -1, 1).
Fig 2.
Flowchart of the image encryption procedure.
Fig 3.
Encryption and decryption results.
(a) Boat (b) Cipher image, (c) Decoded image, (d) Tiffany, (e) Cipher image, (f) Decoded image, (g) Pepper (h) Cipher image, (i) Decoded image.
Table 1.
Key space results comparison with other methods.
Fig 4.
The key sensitivity test: (a) cipher image with x1 changed to x1+10−15; (b) cipher image with x2 changed to x2+10−15; (c) deciphered image with x4 changed to x4+10−15; (d) deciphered image with x5 changed to x5+10−15.
Table 2.
Differences between the cipher and decipher images with minor key modifications.
Fig 5.
Histogram of the plain and cipher images.
(a) Boat's histogram (b) Boat's cipher histogram, (c) Tiffany's histogram, (d) Tiffany's cipher histogram, (e) Pepper's histogram, (f) Pepper's cipher histogram.
Table 3.
Chi-square test of the histograms.
Fig 6.
Correlation between the plain image Pepper and the cipher image in three directions.
(a) Horizontal direction of the plain image, (b) Horizontal direction of the cipher image, (c) Vertical direction of the plain image, (d) Vertical direction of the cipher image, (e) Diagonal direction of the plain image, (f) Diagonal direction of the cipher image.
Table 4.
Correlation coefficients of the adjacent pixels in the Pepper image.
Table 5.
Information entropy of the cipher image.
Table 6.
NPCR and UACI values for cipher images.
Fig 7.
Recovery after different degrees of cropping attacks.
(a) 1/8 cropped, (b) 1/4 cropped, (c) 1/2 cropped, (d) deciphered of (a), (e) deciphered of (b), (f) deciphered of (c).
Fig 8.
Decryption results with different noise.
(a) Gaussian v = 0.001, (b) Gaussian v = 0.005, (c) Gaussian v = 0.01, (d) Salt and pepper d = 0.001, (e) Salt and pepper d = 0.005, (f) Salt and pepper d = 0.01.
Table 7.
PSNR values of different schemes with different percentages of salt and pepper noise.
Table 8.
PSNR values of different schemes with different percentages of data loss.
Table 9.
Comparison of encryption times (seconds).