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Watermarking, steganography and content forensics - · PDF fileWatermarking Steganography Content forensics 2. Ingemar J. Cox Watermarking Watermarking is the practice of imperceptibly

Jul 14, 2018

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  • Watermarking, steganography and content forensics

    Ingemar J. Cox

  • Ingemar J. Cox

    Introduction

    Watermarking

    Steganography

    Content forensics

    2

  • Ingemar J. Cox

    Watermarking

    Watermarking is the practice of imperceptibly altering a Work (image, song, etc.) to embed a

    message about that Work.

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  • Ingemar J. Cox

    Watermarking

    The primary motivation for watermarking has been to protect content

    4

  • Ingemar J. Cox 5

  • Ingemar J. Cox 5

  • Ingemar J. Cox 6

    Muzak: the first commercial watermarking

    The first skyscraper was built in Chicago in 1885

  • Ingemar J. Cox

    Muzak: the first commercial watermarking

    The elevator was an essential element

    In the 1930s passenger elevators were new and frightening Music in elevators was introduced to calm passengers

    Muzak was the dominant supplier

    Nirvana - On a plain

    Rockabye Baby - On a plain

    7

  • Ingemar J. Cox

    Muzak: the first commercial watermarking

    The elevator was an essential element

    In the 1930s passenger elevators were new and frightening Music in elevators was introduced to calm passengers

    Muzak was the dominant supplier

    Nirvana - On a plain

    Rockabye Baby - On a plain

    7

  • Ingemar J. Cox

    Muzak: the first commercial watermarking

    The elevator was an essential element

    In the 1930s passenger elevators were new and frightening Music in elevators was introduced to calm passengers

    Muzak was the dominant supplier

    Nirvana - On a plain

    Rockabye Baby - On a plain

    7

  • Ingemar J. Cox 8

    Muzak: the first commercial watermarking

    Emil Hembrooke, Identification of sound and like signals, US Patent 3,004,104 Filed 1954, Issued 1961

    The present invention makes possible the positive identification of the origin of a musical presentation and thereby constitutes an effective means of preventing such piracy, i.e. it can be likened to a watermark in paper.

    In use until the mid 1980s

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    Applications of digital watermarking

    Broadcast Monitoring Nielsen/Digimarc Teletrax/Philips

    Owner Identification Verimatrix - IPTV Widevine Technologies

    Proof of Ownership

    Transaction Tracking Thomson/Technicolor (Philips) - Oscar screeners Cinea/Dolby - Digital cinema

  • Ingemar J. Cox

    Applications of digital watermarking

    Content Authentication Signum Technologies

    Copy Control Verance - HD-DVD, DVD-audio

    Legacy systems Tektronix - syncing sound and video (lipsync) MarkAny - syncing lyrics with music (mp3 players)

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  • Ingemar J. Cox

    Watermarking

    Why not use cryptography?

    Cryptography assumes:1. Alice and Bob trust one another2. Communication between Alice and Bob succeeds

    However, Alice (Hollywood) cannot trust Bob (consumer) And if communication fails, watermark protection fails

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  • Ingemar J. Cox

    Watermarking

    Watermarking is NOT cryptography

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  • Ingemar J. Cox

    Watermarking

    Watermarking IS communications

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  • Ingemar J. Cox

    Watermarking

    The content is more important than the message

    So the watermark/message must be imperceptible

    And often, the message payload is small

    But, to be practical, a watermark must also be robust

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    Watermarking

    Spread spectrum communications content modeled as noise

    high noise regime

    Communications with side information content modeled as side information

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    Watermarking as communications

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    Transmitter Receiver+

    Noise

    message, mmessage, m x y

    x is limited by a power constraint x2[i] p

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    Watermarking as communications

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    Embedder Detector

    Noise

    message, m message, mx y+ +

    Noise

    x is limited by a power constraint x2[i] p

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    Spread spectrum communications

    Requirements: Unobtrusive Survive common distortions

    E.g. lossy compression

    Spread spectrum communications Originally developed for military communications

    Difficult for enemy to detect Difficult for enemy to jam

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    Spread spectrum communications

    Lets consider embedding an 8-bit message in an image 01100101

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    Spread spectrum communications

    Since we have an 8-bit message Spread each bit over all pixels

    Spread spectrum watermarking

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    Spread spectrum communications

    Each bit is represented by a chip sequence A pseudo random number sequence

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    Spread spectrum communications

    10 101 0 1 0

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    Spread spectrum communications

    Detect each bit using linear correlation

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    Spread spectrum communications

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    Spread spectrum communications

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    Spread spectrum communications

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    Spread spectrum communications

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    Spread spectrum communications

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    Spread spectrum communications

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    Spread spectrum communications

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    Spread spectrum communications

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    Spread spectrum communications

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    Perceptual modelling

    In the previous example, the random pattern was added equally to all parts of the image

    But some areas are more (less) sensitive than others

    We can identify these areas using perceptual models Same models used for lossy compression

    Must embed in perceptually SIGNIFICANT regions to be robust to lossy compression

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    Original image

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    No perceptual modeling

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    Perceptual modeling

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    Original image

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    Communications with side information

    Spread spectrum watermarking models the cover Work as noise

    However, the cover Work is Not random Completely known at the time of embedding

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    Watermarking as communications

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    Embedder Detector

    Noise

    message, m message, mx y+ +

    Noise

    x is limited by a power constraint x2[i] p

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    Watermarking as communications

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    Embedder Detector

    Noise

    message, m message, mx y+ +

    Noise

    x is limited by a power constraint x2[i] p

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