Fig. 1. Decryption principle of position-multiplexing-based double-image encryption in CDPE. (a) Decryption of plaintext image 1; (b) decryption of plaintext image 2

Fig. 2. Encryption algorithm for position-multiplexing-based double-image encryption in CDPE

Fig. 3. Numerical demonstration of effectiveness of proposed method. (a)(b) Two plaintext images; (c) KM; (d) CM; (e)(f) two decrypted images; (g) dependence of error function on iteration number

Fig. 4. Dependence of decrypted plaintext quality on ratio of correct pixel number in KM

Fig. 5. Dependence of decrypted image quality on wavelength error. (a) BJUT; (b) NYNU

Fig. 6. Dependence of decrypted image quality on distance errors. Dependence of decrypted "BJUT" on (a) Δd1 and (b) Δd2; dependence of decrypted "NYNU" on (c) Δd3 and (d) Δd4

Fig. 7. Decrypted results when Δd takes different values in case of d1=d2=200mm. (a)(b) Δd=0.1mm; (c)(d) Δd=0.4mm;(e)(f) Δd=1.0mm; (g)(h) Δd=2.0mm

Fig. 8. Numerical demonstration of proposed method for grayscale image encryption. (a)(b) Two plaintext images; (c) KM; (d) CM; (e)(f) two decrypted images; (g) dependence of error function on iteration number

Fig. 9. Decryption scheme and results after extension of proposed method to triple-image encryption. (a)-(c) Decryption scheme of three plaintext images; (d)-(f) decrypted results of three plaintext images

Fig. 10. Decrypted images for polluted ciphertexts obtained by proposed method. (a)(b) β=0.1; (c)(d) β=0.3; (e)(f) β=0.5;(g)(h) β=0.7

Fig. 11. Results of CPA for proposed method. (a) Recovered key mask; (b) (c) decrypted results of Fig. 3(d) with recovered key mask; (d) (e) decrypted results of Fig. 8(d) with recovered key mask

Fig. 12. Experimental setup for decryption

Fig. 13. Experimental demonstration of effectiveness of proposed method. (a)(b) Two POI images displayed on SLM; (c)(d) decrypted images

Fig. 14. Experimentally decrypted results when Δd takes different values. (a)(b) Δd=0.1mm; (c)(d) Δd=0.4mm; (e)(f) Δd=1.0mm; (g)(h) Δd=2.0mm