Optical encryption based on double random-phase encoding: secure versus unsecure variants

Area of Science:

• Cryptography
• Information Security
• Optical Engineering

Background:

• Double Random-Phase Encoding (DRPE) is a cryptosystem susceptible to brute-force attacks.
• Key-sensitivity analysis often reveals vulnerabilities in cryptosystems.
• The smoothness of Mean Squared Error (MSE) and Correlation Coefficient (CC) curves was an unreported vulnerability in DRPE.

Purpose of the Study:

• To present a smart brute-force attack targeting DRPE.
• To identify and analyze an unreported vulnerability in DRPE's key-sensitivity analysis.
• To propose a defense mechanism against this novel attack.

Main Methods:

• A brute-force attack exploiting the smoothness of MSE and CC curves was developed.
• Key-sensitivity analysis was used to visualize the vulnerability.
• Modular arithmetic pre-coding was implemented as a countermeasure.

Main Results:

• The study demonstrated a new vulnerability in DRPE based on smooth MSE and CC curves.
• Modular arithmetic pre-coding significantly increased robustness against the presented attack.
• Pre-coding resulted in highly nonlinear and oscillatory MSE and CC curves in the key space.

Conclusions:

• The identified vulnerability in DRPE can be exploited by a smart brute-force attack.
• Modular arithmetic pre-coding is an effective defense, enhancing DRPE security.
• Understanding this vulnerability improves the design and robustness analysis of DRPE systems.