Image Compression and Encryption Using Discrete Fractional Cosine Transform

Abstract

Digital image processing techniques are used to enhance the quality of image and to reduce the data needed to represent the image without visually affecting the quality of image. The objective of compression is to reduce the data volume and achieve reproduction of the original data without any perceived loss in data quality. Applications of compression include digital imaging. Compression of medical images for efficient use of storage space and transmission bit rate has become a necessity. Cryptographic techniques are used to scramble images so that an adversary could not the original image without knowing the secret key. The objective of encryption is to transform data into an unreadable form to ensure privacy. Encryption was widely used in military imaging for secure transmission of information. Today, however, encryption is widely used by everyone to transmit information such as commercial transactions (exchange of credit card information, etc.). In the case of the former, the "compressed" data needs to be uncompressed to the original form while in the case of the latter; the "encrypted" data needs to be decrypted to the original form. 1.1 IMAGE COMPRESSION Today transmitting multimedia material in uncompressed form is completely out of question. The only hope is that massive compression is possible. Fortunately a large body of