Integrity of multimedia data ● Techniques for digital watermarking ● An example in the Wavelet domain ● Experimental results: evaluation

Watermarking ● Basic idea To insert a invisibile structure (watermark) inside a «host» signal in order to mark it ● Result Author identification Author identification Which alteration? Which quality? Which alteration? Which quality? Evalutaion of the similarity between the original and teh altered data Evalutaion of the similarity between the original and teh altered data

Applications Applicazioni Copyright Protection Authentication Hidden annotation Secret communication E-commerceVideo-on-demandE-commerceforensic Multimedia distributuion medical imaging cartograpgy indexing & retrievial Military and intelligence Alternatives to cryprography

Example ● Method Request analysis Request analysis Choice of watermarking techniques Choice of watermarking techniques Improvements on the state-of-the- art Improvements on the state-of-the- art

Method ● «musts» Do not compromise the image quality Do not compromise the image quality Capable to reveal unauthorized modification Capable to reveal unauthorized modification JPEG2000 compression is «legal» JPEG2000 compression is «legal» unauthorized modifications are difficult unauthorized modifications are difficult To localize altered area To localize altered area

Robust self-embedding watermarking Method ● Tecnica di watermarking Fase di CASTING Fase di DETECTION Confronto

Method ● Improvements Watermark is less visible Watermark is less visible Correct thealterations Correct thealterations Resistant to JPEG 2000 compression Resistant to JPEG 2000 compression

The algorithm: casting Self Embedding DWT Correction error code Quantization and binarization IDWT DWT Quantization and binarization

Self Embedding DWT Codice a correzione d’errore Quantization and binarization Quantization and binarization IDWT The algorithm: casting Quantization function

Casting Correction error code Parity Bit 01001…011 Base band Self Embedding DWT Correction error code Quantization and binarization IDWT

Casting Binary Code Golay (23,12) … v 0 12 … Self Embedding DWT Correction error code Quantization and binarization IDWT

IDWT Casting Low Bit Modulation (LBM) Test on JPEG2000 Coefficienti wavelet autenticati Coefficienti wavelet per inserimento watermark Coefficienti wavelet non utilizzati Self Embedding DWT Correction error code Quantization and binarization IDWT

Detection W Extraction DWT Quantization and Binary representation Error correction code Golay (23,12) … v 0 12 …

● Which Metric? ● Evaluation of watermarking percetion ● Evaluation of robustness ● How to reveal and correct alterations? Experimental results ● Which images?

Test Images Medical Syntethic Standard Naturalistics 62 images in 4 categories

Metrics Similarity between watermark Similarity between images

Is it visible? 3 Livelli di decomposizione 5 Livelli di decomposizione Immagine Originale Risultati sperimentali 3 Livelli di decomposizione 5 Livelli di decomposizione

Experimental results What about robustness??? Simple attacks Simple attacks Gaussian noise Gaussian noise Median filter Median filter Gaussian filter Gaussian filter lossy compression JPEG2000 lossy compression JPEG2000 removal attacks removal attacks Removal of watermark Removal of watermark removal of an area of the image removal of an area of the image Loss of synchronization Loss of synchronization

Robustness to compression JPEG2000 Simple attacks

Removal of an area of the images PSNR Difference PSNR Removal attacks

Experiments Removal and corrections Immagine originaleImmagine marchiata e compressa Immagine manipolataErrori rilevatiErrori rilevati nel dominio spazialeErrori rilevati nel dominio DWTImmagine ricostruita