11-04-2014, 01:09 PM
Crypto-watermarking For medical image Safe transfer
INTRODUCTION
Now a days, image , video and 3D object security becomes increasingly important for many applications.
For example:
confidential transmission , video surveillance, military and medical applications.
A new method that combines image encryption and watermarking technique for safe transmission purpose.
This method is based on the combination of public private keys and secret key ciphering, and watermarking
Crypto watermarking = encryption + digital watermarking
Encryption:
Encryption is the conversion of data into a form, called a ciphertext, that cannot be easily understood by unauthorized people.
steps for traditional encryption
1] image is encrypted with secret key
2] key is encrypted with public key
Both encrypted image and encrypted key are transferred separately.
IMAGE ENCRYPTION BY STREAM CYPHER
For every pixel p(n) of the original image, if k is the length of the key , we calculate the pixel value p’(n) of the ciphering image using the equation:
P’(n)=p(n)+a(1)p’(n-1)+a(2)p’(n-2)+….+a(k-1)p’(n-k-1) +a(k)p’(n-k)
For every pixel, the encryption depends previously of the original pixel value, of the key, and of the k pixels previously ciphered.
Watermarking:
Watermarking is the process of embedding information into an image or video which may be used to verify its authenticity or the identity of its owners.
Digital watermarking is , water marking applied to digital signal.
1]visible watermarking
2] invisible watermarking
Transmission
The original image is encrypted using a secret key.
The secret key K is encrypted using private key.
It is again encrypted using public key.
This encrypted key is watermarked with encrypted image and transferred to the network.
Reception
The transferred encrypted image is received and the secret key is extracted.
Then it is stream ciphered to obtain the original image.