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By:

Nitin Mathur

EC-B

Roll No. -76

ASeminar presentation

On IMAGE AUTHENTICATION TECHNIQUE

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Image Authentication

• By data authentication we mean here a procedure capable of ensuring that data have not been tampered with and of indicating their true origin.

• There are two types of authentication schemes, which are-

1. Cryptographic data authentication.-

2. Watermarking-based authentication.

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Cryptography

• a straight forward way to provide video authentication, namely through the joint use of asymmetric key encryption and the digital Hash function

• It has mainly two functions:-> Encryption-> Decryption

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Encryption & Decryption

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Cryptographic Data Authentication

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Drawbacks of Cryptographic Authentication

• Knowledge of private key • Delay in transmission • High requirements of video camera

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Watermarking

What is a “Digital Image Watermark”

1. pattern inserted into a digital image

2. may be unique to each copy, or be common to multiple copies

A given Watermark may be 1.Unique to each copy (e.g., to identify the intended recipient), or 2.Be common to multiple copies (e.g., to identify the document source)

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Types of Watermarking

WATERMARKING

FRAGILE WATERMARKING

ROBUST WATERMARKING

INVISIBLEWATERMARKING

VISIBLE WATERMARKING

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Requirements of Watermarks

1. The watermark must be difficult or impossible to remove

2. The watermark must survive image modifications that are common to typical image-processing applications

3. An invisible watermark should be imperceptible so as not to affect the experience of viewing the image.

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Techniques of watermarking

• Spatial watermarking

• Frequency watermarking

-> by superimposing a symbol over an area of the picture.

-> be applied using color separation

-> applying a transforms like the Fast Fourier Transform (FFT), Discrete Cosine Transforms (DCT), Wavelet Transforms etc.

-> Watermark signal is applied to lower frequencies.

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The FFT Watermarking

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The Image Authentication Framework

• Watermark Embedding

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The Image Authentication Framework

• Watermark Detection

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ADVANTAGES

• Robustness to high quality lossy image compression.• Automatic discrimination between malicious and innocuous

manipulations.• Controllable visual deterioration of the VS sequence by

varying the watermark embedding power.

DISADVANTAGES

• Frame independent watermark can be easily found by comparative analysis of all image sequence •The detector should know the frame number in order to perform authenticity check.

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THANK YOU