# VI. Conclusion and Future Work

## Conclusion

We have presented an end-to-end AI pipeline for detecting digitally replicated signatures in financial audit reports at scale.
Applied to 90,282 audit reports from Taiwanese publicly listed companies spanning 2013--2023, our system extracted and analyzed 182,328 CPA signatures using a combination of VLM-based page identification, YOLO-based signature detection, deep feature extraction, and dual-method similarity verification.

Our key findings are threefold.
First, we argued that signature replication detection is a distinct problem from signature forgery detection, requiring different analytical tools focused on intra-signer similarity distributions.
Second, we showed that combining cosine similarity of deep features with difference hashing is essential for meaningful classification---among 71,656 documents with high feature-level similarity, the structural verification layer revealed that only 41% exhibit converging replication evidence, while 7% show no structural corroboration despite near-identical features, demonstrating that a single-metric approach conflates style consistency with digital duplication.
Third, we introduced a calibration methodology using a known-replication reference group whose distributional characteristics (dHash median = 5, 95th percentile = 15) directly informed the classification thresholds, achieving 96.9% capture of the calibration group.

An ablation study comparing three feature extraction backbones (ResNet-50, VGG-16, EfficientNet-B0) confirmed that ResNet-50 offers the best balance of discriminative power, classification stability, and computational efficiency for this task.

## Future Work

Several directions merit further investigation.
Domain-adapted feature extractors, trained or fine-tuned on signature-specific datasets, may improve discriminative performance beyond the transferred ImageNet features used in this study.
Temporal analysis of signature similarity trends---tracking how individual CPAs' similarity profiles evolve over years---could reveal transitions between genuine signing and digital replication practices.
The pipeline's applicability to other jurisdictions and document types (e.g., corporate filings in other countries, legal documents, medical records) warrants exploration.
Finally, integration with regulatory monitoring systems and small-scale ground truth validation through expert review would strengthen the practical deployment potential of this approach.
