Image compression and encryption has been a great area of interest since images are being used as one of the most valuable information source in many areas like medical application, military application, space science application and many more. There are three types of image namely binary image, grayscale image and colour image. Binary image has only two intensity levels black and white, whereas grayscale images have 256 intensity level and colour images have various colour map each of which have 256 intensity levels. For the being here the area of interest is grayscale image.
Now the first question that arises is what is image compression and encryption and why it is needed? Image compression means reducing the size of an image without or with a certain loss of data. This is needed because for an image which need to be transmitted over a channel will consume a large bandwidth according to its size. So if the size can be reduced the bandwidth needed for the transmission of the compressed image will be less. Encryption on the other hand is needed to provide security to the information. This is a method or a process for protecting information from undesirable attacks by converting it into a form non recognizable by its attackers. Data encryption mainly is the scrambling of the content of data, such as text, image, audio, video and so forth to make the data unreadable, invisible or incomprehensible during transmission. The goal is to protect the content of the data against the attackers. The reverse of data encryption is data decryption, which recovers the original data.
1.1 IMAGE COMPRESSION :
1.1.1 IMAGE:
An image is actually a 2-D signal processed by the human visual system. The signals representing pictures area unit sometime...
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...m. In symmetric key there is a single key that is used in both ends to encrypt and decrypt a data. But in case of asymmetric key there are two keys that are used in the algorithm namely public key and private key.
Here in case of image encryption symmetric key algorithm has been used.
1.3.2 IMAGE ENCRYPTION USING SCAN PATTERNS
The proposed image encryption method is actually based on the rearrangement of the pixels of an image. The rearrangement is achieved by the scan patterns and it is also used as the key for both encryption and decryption. At first the image has been divided into eight bit planes and in each bit plane different scan patterns has been used to rearrange the pixel in order to encrypt it.
So for each bit plane there are a separate key to decrypt it. A detail discussion about scan patterns and scan paths has been presented in the next chapter.
What is encryption? Encryption is a technological technique that protects and secures the transfer of plain text information between two sources through the use of the internet. This is done by rearranging the text using a mathematical algorithm that renovates the message into an indecipherable form, which can only be unlocked and translated with a use of a key. The strength of the encryption key is measured by its length, which is determined by the number of bits and by the type of encryption program.
Asymmetric Encryption is used to protect the data while in movement. Asymmetric Encryption is also known as Public Key Encryption. It uses two related keys, a public key and a private key which is not shared with anyone. This pair of keys are developed by mathematical methods which can be solved in one direction. So anyone can encode a data using the public key but only the user with a private key can decode that specific data. The length of Asymmetric Key Encryption is normally 1024 or 2048 bits. However, in Asymmetric framework the keys with smaller than 2048bits are considered as not safe to use.
Encryption is a strategy for changing data on a computer in a manner that it gets to be distinctly incomprehensible regardless of the possibility that somebody can access a PC with individual information on it.
When we take a closer look at the picture, we are able to depict symbols that will means something to us, it is called the paradigmatic analysis. You are able to comprehend a
A camera lens focuses patterns of light onto film which records the image exactly. If the lens is out of focus or partially covered, a b lurry or obscured picture will result. The film is a recording device, it does not interpret and select what it portrays. Images from a camera are objective in a very literal sense. Seeing, however, is not such a seamless process. Our eyes work similarly to a camera in that they have a lens which focuses a real image on our retina, a light sensitive sheet of cells. This retinal image is a portrayal of the world as it truly is. The image which we see, however, is not this image. By considering a normal vis ual property as well as an uncommon ocular disorder the process of formulating our visual sense will be investigated. There is a difference between the picture recorded on film and that recorded by our brains. For purposes of this paper, the term "retina l image" is used as an analogy to a photographic image (one without interpretation by the brain). The phrase "brain image" refers to the retinal image post-brain interpretation. The brain image is the image which would be described by the person, the imag e which is thought of as seeing.
In this case, the units containing the information underlying our use of a word, are called logogens and encompass the verbal system. Whereas, imagens are the units in the dual-coding theory containing information that produces the mental image which make up the non-verbal system. Thus, as I think of the lyrics being sung by the artist, for example the word fireside, it may invoke a mental image of firewood or even an image of my family and I watching christmas movies by the fire. This would represent an example of a mental image that was produced by logogens, in which a similar situation can produce a mental image but instead, imagens are
Encryption: - Data encryption is the best way to reduce risks associated with misplaced, lost or stolen data.
Is it like a language or not? How do visual images work? It is important to study and understand visual images. That’s exactly what semiology analysis consists of. It's a set of concepts which produce accounts of the way the meanings of images are produced through the images.
Data Encryption is from the cryptography science, which includes coding and decoding of message to protect the safety. Development computer technology makes the encryption even more complicated. The ability for people to break codes is increasing, so are the ability to guard the codes. Many encryptions are available now. They were developed by some hi-tech company and sold, or you can choose some free service. Actually, when you are using the web browsers, emails, or even the basic system, your information has been automatically encrypted.
There are two keys to successful imaging - these are vividness and controllability and they are acquired through practice. As our notes states, the greater the number of senses that can be used during imagery-
Computer science is a vast field that includes nearly everything relating to computers. Everyday there is information transmitted all over the Internet. Pictures are uploaded, transactions are made on thousands of online retail websites, and banking transactions take place everyday on the Internet. All of these transactions have created a need for secure communications. People wish to keep things like banking, medical, and political information from the eyes of unwelcome parties. This has created a need for cryptography. Cryptography is the science or study of the techniques of secret writing, especially code and cipher systems, and is used by everyone from the average citizen to the government and military.
Data encryption refers to the transformation of data into a structure that makes it unreadable by anyone without a secret decryption key. It ensures that messages can be read only by the planned recipient. Encryption is the procedure of obscuring information to create it unreadable without special information. Only organizations and individuals with an abnormal need for secrecy have actually made good use of it. Nowadays, encryption is one of the most important technologies for maintaining your privacy and the security of important information. This helps out greatly especially when E-Commerce is being used.
The internet allows people to communicate sensitive information, and if received in the wrong hands can cause many problems for that person. Cryptography is the study or science of techniques of secret writing and message hiding. Cryptography constitutes any method in which someone attempts to hide a message, or the meaning, in some medium. One specific element of cryptography is encryption, which hides the data or information by transforming it into undecipherable code. Encryption uses a specified key to perform the data transformation.
Thus giving priority to the important vectors higher compression can be achieved at better quality. The algorithm is also useful for embedded vector quantization coding of wavelet coefficients. INTRODUCTION lmage compression reduces the data for image representation. lmage compression techniques are divided into two main categories Transform techniques and nontransform techniquesh transform techniques compression is achieved by encoding the transformed coefficients. Compression based on wavelet transform decomposes the image in four subbands.
Such a blocking signature can served as an evidence of JPEG compression [2], and some tampering operations [3]. Another important property is the quantization artifacts in the DCT frequency domain. During JPEG compression, each DCT frequency component in the 8 × 8 block is quantized by a quantization step. It will lead to a specific shape of the corresponding DCT histogram.