<![CDATA[Business document forgery and email phishing have been significantly amplified by generative artificial intelligence, yet existing security frameworks address communication-channel protection and document authentication as separate concerns, leaving organizations vulnerable to coordinated multi-vector attacks. This research aims to design, implement, and evaluate a unified "Dual-Shield" framework that bridges this gap through an integrated, lightweight solution for real-time business operations. The proposed system combines a four-stage email security gateway—covering sender verification, URL analysis via VirusTotal API, and attachment sanitization—with a dual-layer digital watermarking engine applied to transaction receipt images. The watermarking component pairs a robust Discrete Wavelet Transform–Singular Value Decomposition layer for authorship attribution with a semi-fragile Quantization Index Modulation–Discrete Cosine Transform layer for monetary integrity verification, assessed via imperceptibility, robustness, and tamper-detection metrics on synthetic and real-world datasets. Results show the robust watermark achieved peak signal-to-noise ratio values of 43.38–43.48 dB with SSIM above 0.98. All generative AI manipulations were detected with bit error rates of 0.375–0.472, and targeted ten-percent numerical fraud was identified by the semi-fragile layer. The gateway correctly classified all test scenarios, confirming that malicious URL detection overrides trusted sender status to prevent whitelist exploitation.]]>
