We study the encryption and decryption processes of color images using thesynchronization of polarization dynamics in a free-running vertical-cavitysurface-emitting laser (VCSEL). Here, we consider a bidirectional master-slaveconfiguration or two-way coupling with two VCSELs. The latter are shown toexhibit hyperchaos and synchronization with a high level of similarity betweentheir emission characteristics. The coupled VCSELs are then used as atransmitter and a receiver for the communication of image or data. Furthermore,we propose a modified chaos-based image encryption algorithm using the pixel-and bit-level permutations which provides robust, faster and simplerencryption/decryption compared to many other chaos-based cryptosystems. Theperformances of the new cryptosystem are analyzed and compared with a recentlydeveloped scheme [Opt. Las. Eng. 90 (2017) 238-246]. The security analysis andsome statistical investigations show that the proposed cryptosystem isresistant to various types of attacks and is efficient for securecommunications in nonlinear optical media.
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