A singular-value-based semi-fragile watermarking scheme for image content authentication with tamper localization

• Utilize relationships of singular values to extract content-dependent watermark.
• Merge relationships of singular values to choose adaptive quantizer for each block.
• Apply adaptive quantization to embed secure watermark in the wavelet domain.
• Define a 3-level authentication process to detect authenticity and prove tampering.
• Use five measures to compensate misclassification and capture distortions.

This paper presents a singular-value-based semi-fragile watermarking scheme for image content authentication. The proposed scheme generates secure watermark by performing a logical operation on content-dependent watermark generated by a singular-value-based sequence and content-independent watermark generated by a private-key-based sequence. It next employs the adaptive quantization method to embed secure watermark in approximation subband of each 4 × 4 block to generate the watermarked image. The watermark extraction process then extracts watermark using the parity of quantization results from the probe image. The authentication process starts with regenerating secure watermark following the same process. It then constructs error maps to compute five authentication measures and performs a three-level process to authenticate image content and localize tampered areas. Extensive experimental results show that the proposed scheme outperforms five peer schemes and its two variant systems and is capable of identifying intentional tampering, incidental modification, and localizing tampered regions under mild to severe content-preserving modifications.