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With the rapid advancement of the digital technology, electronic and electronic devices are widespread used in our daily life. Electronic has become an integral part in today's society. Almost every sector of the world's population exposed to numerous source of electronic devices to perform the require task. In fact, it is quite safe to say that the world is now all circulated by the electronics and electronic devices have become inseparable from human life.
From daily used items in office as well as household such as computer, portable media player, digital cameras, television, fax machine and mobile telephone to the automated welding machine used in industry, the usage of the electronic has dominated in our daily chores and continuously growth significantly. In order to cater the demand of the electronic consumers, a huge variety of electronic products have been designed and manufactured.
With the advance towards a paper-less society, computer has used to perform designing, storing critical content/information, circuit diagram and so on which is highly copyright/trade secret that strictly not allow to spread out from one to another over the industry or outside the company. In electronic industry, schematic design diagram are the great design essences of all the electronic devices. It is also an asset of the electronic industry which is important and confidential to the company. Circuit diagram are the painstaking work of the design engineer which is crucial and necessary to protect and prevent from unauthorized access. Due to the increasingly design of the electronic product and widely using images in industrial process, the information security on the storage of circuit diagram as well as its transmission is the key challenge and concerned for today's society.
In order to protect the confidential circuit diagram from unauthorized access, the scheme of circuit design diagram encryption and decryption system is implemented to ensure that unauthorized copied of the files are useless to the person who copies them since the files are being encrypted and in unreadable form.
Image encryption is a technique to convert the original image to an unreadable form of picture, in such an extent, prevent the content of the images from being revealed by unauthorized user that without the decryption key.
Generally, there are three major categories of image encryption algorithms which are classified and shown in below:
Position permutation based algorithms 
Value transformation based algorithms 
Visual transformation based algorithms 
Plain image: An original image before going through the encryption process.
Cipher image: An encrypted /unreadable image after an encrypting process.
Encryption or Enciphering: The process of converting the original image to the encrypted image is called encryption or enciphering.
Decryption or Deciphering: The process of restoring the encrypted image back to the original image is called decryption or deciphering.
Cryptography: Cryptography is an area of study of keeping the information secret, often referred to the technology of encryption.
Basic system of cryptography
Cryptography can be classified into two types called private key cryptography and public key cryptography.
Private Key Cryptography:
Private key cryptography can be defined as symmetric key cryptography. With private key cryptography system, both the sender who encrypts the information and receiver who decrypts the information must use the same key.
Public Key Cryptography:
Public key cryptography is also known as asymmetric key cryptography. With public key cryptography system, two mathematical of the related key are generated by using the encryption algorithm. Information that encrypted by the sender using the public key can only be decrypted by the receiver using other key (secret key).
In short, cryptography technique is needed when information is being transferred/transmitted along an unsecured communication line/network or being stored in an unsecured system. Cryptography technique make used of the encryption algorithms to perform the encryption process.
Background idea of image encryption proposed in this scheme
In computerized system, image can be view as a block or arrangement of a different color pixel's value. The correlation among the pixels forms a comprehensible image. An advancement of the image processing technology enable user to write a program to control and manipulate the pixel's value of the picture. By scrambling and shuffle the image pixel's value, the encryption effect of disrupting the order of the image' pixel can be achieved. Thus, reduced the correlation of the pixels and decreased the perceptual information of the image.
Figure 1: Structure of Digital Images
Problem and Motivation
There are many algorithms have been proposed by researcher, each technique has its own advantages and limitation.
A study of image encryption is a crucial part to prevent unauthorized illegal access to the circuit design diagram in electronic industry. This paper proposes an idea of using scan based algorithms to perform the encryption process. Contrasting to the ordinary encryption process, the proposed algorithms enhanced the scan based algorithms by adding in digital watermarking as a feature in hiding the encrypted picture. Thus, provide double protection to the original schematic diagram.
Block Diagram of the proposed image encryption approach:
SCAN Based Encryption
Figure 2: Block diagram of the proposed image encryption approach using SCAN patterns and Watermarking
The aim of the project is to develop a digital image processing software that has ability to perform encryption and decryption in term of its accuracy and efficiency (speed) compare to the existing techniques.
To investigate and understand the digital image processing process chain.
To research and evaluate the algorithm of the various encryption technique for the picture encryption.
To use MATLAB as a tools to develop and implement circuit diagram encryption and decryption.
To research and evaluate the algorithm of the various watermarking technique for picture hiding.