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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