Forged seal detection based on the seal overlay metric

Area of Science:

• Forensic Science
• Document Examination
• Image Analysis

Background:

• Authenticating official documents often relies on verifying the integrity of seal impressions.
• Traditional methods can be challenged by advanced forgery techniques like lithography and computer-aided manufacturing.
• A quantitative and robust method is needed to assess seal impression authenticity.

Purpose of the Study:

• To develop and validate a new method for verifying the authenticity of seal impressions on documents.
• To introduce the seal overlay metric for quantitative assessment of seal impression quality and similarity.
• To improve the detection rate of sophisticated forged seals.

Main Methods:

• A reference seal pattern is generated from multiple high-quality genuine impressions.
• Target seal impressions are segmented from background noise using adaptive thresholding.
• Spatial alignment and computation of the seal overlay metric between reference and target impressions.
• Adjustment of the seal overlay metric by the filling rate to account for impression quality.

Main Results:

• The proposed seal overlay metric effectively quantifies the similarity between a target seal and a genuine reference seal.
• The method demonstrated high accuracy in detecting forged seals, including those produced by advanced techniques.
• Adjusting the metric by the filling rate reduced misclassification rates.

Conclusions:

• The seal overlay metric provides a reliable approach for authenticating seal impressions.
• The method is effective against advanced forgery techniques, enhancing document security.
• This technique offers a valuable tool for forensic document examiners.