# Quantum-Secure Coherent Optical Networking for Advanced Infrastructures in Industry 4.0
## 5 Comparative Analysis of Optical Encryption Methods  
A comparative analysis of leading optical encryption techniques occurs in this section according to Section 3's identified weaknesses. This evaluation applies an iterative case-based approach [32] and assesses the methods under classical and post-quantum circumstances. The research established findings about each method's bandwidth abilities and operational constraints by assessing documented specifications together with laboratory test data and reported exploits [33]. The evaluation validated by an iterative approach required several danger simulations that demonstrated each method's performance against integrated hardware-based as well as protocol-level attacks, starting from minimal side-channel listening to quantum-aided codebreaking [34]. A systematic methodology enables the establishment of which encryption approaches can handle vulnerabilities, including overhead byte manipulation, synchronization gaps, and advanced phase manipulations. Improved cryptographic methods in optical networks have emerged because of rising security demands for data protection. The protection of high-speed data goes beyond conventional methods to use fundamental light physics and in certain instances depends on quantum mechanical principles. System encryption at the physical level eliminates specific attack routes that target overhead fields and DSP routines. Both approaches conform to the CIA model [30] but share individual technical difficulties, as outlined in the systematic evaluation guidelines [35]. Figure 7: Optical signal interception and manipulation system. Double Random Phase Encryption (DRPE) stands as one of the most researched optical encryption methods due to its wide scientific investigation. Two separate random phase masks serve as the core elements in DRPE and implement positioning in the input plane and the Fourier plane of an optical device. Previous research conducted used this technique within a specific case unit and executed the experiments to validate the findings in Section 3[32]. The theoretical security level of DRPE depends on specific parameters, yet the validation [34] showed that deep neural parameters [36] utilized in advanced ciphertext-only attacks pose significant threats to the system. The attacks discover a method to reverse random phase transformations, leading to the unauthorized recovery of data while omitting necessary encryption keys. Official protocol descriptions with DRPE deployment reports to demonstrate DRPE phase masks fall victim to learning attacks, thus causing detrimental performance issues in fast networks [1]. Block-based optical color image encryption, which solves several weaknesses of DRPE by conducting an independent block-based processing of data segments, was introduced in previous research [37]. Systematic testing [32] indicates that data block segmentation enables attackers to face greater challenges because each block introduces randomized features, which prevents some deep-learning attacks from succeeding. According to scenario analysis, the performance of block-based encryption remains stable for shorter times but fails to protect 400G network data at high transmission speed rates [34]. Utilizing this method to reset phase parameters results in the accumulation of overhead, which restricts the scalability of coherent systems operating at a large scale. According to current research, the optical phase mask encoding with multi-homodyne coherent detection (MHCD) method functions as a diagnostic test model for full assessment. Previous work [38] demonstrated that MHCD shifts the signal into high levels of noise, which renders unauthorized decryption practically impossible. Research has used metasurface-based methodologies as an additional method of investigation. The transformation of phase-change metasurfaces described in the previous work in [39] delivers fast tuning capabilities through controlled manipulations of specialized materials to encrypt data.