IMAGE AUTHENTICATION TECHNIQUES

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A Seminar presentation On IMAGE AUTHENTICATION TECHNIQUE

By: Nitin Mathur EC-B Roll No. -76
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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 are1. 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 ³Digital 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

INVISIBLE WATERMARKING

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
-> by superimposing a symbol over an area of the picture. -> be applied using color separation

‡ Frequency watermarking
-> 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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