Security enhancement of color image cryptosystem by optical interference principle and spiral phase encoding

Area of Science:

• Optics
• Cryptography
• Information Security

Background:

• Conventional optical cryptosystems often use random phase masks, which can be vulnerable.
• Spiral phase masks (SPMs) offer advantages due to their ability to store multiple keys within a single mask.

Purpose of the Study:

• To propose a novel color information cryptosystem leveraging optical interference and spiral phase encoding.
• To enhance security and key management in optical encryption systems.

Main Methods:

• Color images are decomposed into RGB channels to prevent crosstalk.
• Each channel is encoded into a spiral phase mask (SPM), generating two spiral phase-only masks (SPOMs).
• SPOMs are phase-truncated for encryption and amplitude-truncated to create asymmetric phase keys, with construction parameters also serving as keys.

Main Results:

• The system effectively decomposes color images into RGB channels, minimizing crosstalk.
• Multiple keys (SPOMs and phase keys) are generated and can be distributed among users.
• The cryptosystem demonstrates high security, as losing even one of the eight keys prevents image retrieval.

Conclusions:

• The proposed spiral phase encoding method provides a robust and secure color image cryptosystem.
• The technique avoids iterative encoding and complex optical alignment, simplifying implementation.
• Numerical simulations validate the feasibility and effectiveness of the proposed optical encryption method.