Abstract
According to encrypting principles of digital images, integrating the characteristic of JPEG image, and using discrete chaotic sequence, this paper has studied encryption and decryption of JPEG image, and has compared and analyzed the corresponding relations between the encryption and decryption effects and their security of two different encrypting schemes of the JPEG image chaotic encryption studied by this paper. In a basic unit of an 8 × 8 data block, image encryption and decryption not only are fast, but also match with JPEG format. The JPEG image encryption can meet the security requirement of the storage and transmission of JPEG images in some common application occasions, and provides an effective and feasible way of encrypting JPEG images.
1. Introduction
The fundamental measure to ensure the security of electronic information is to encrypt it. Image encryption is an important research realm of information encryption. JPEG image is a common compression format of image files applied in the storage and the transmission of images, which greatly saves the storage space and the transmission band of images. Therefore, researches on the encryption and decryption of JPEG images have an important value of theoretic researches and practical applications. On the basis of studying and analyzing the structural feature of JPEG image, according to the basic encryption principles andmethods of digital images, utilizing the stochastic characteristic of chaotic sequences, this paper has studied an effective and feasible method for encryption and decryption of JPEG image, and has analyzed the performances of the chaotic encryption algorithm.
6. Conclusions
The JPEG image encryption studied by this paper considers the feature of the JPEG image compression, and scrambles the image in a basic unit of an 8 × 8 data block, not only greatly decreases the operations of the image encryption and decryption, but also makes the size of the encrypted image file or the decrypted image file keep basically accordant with the one of the original image file. The encryption algorithm is comparatively fit for encrypting bigger JPEG image files, and is not comparatively fit for encrypting smaller JPEG image files. This is because that it cannot ensure enough security of smaller encrypted JPEG images. The two encryption and decryption procedures and performances corresponding to the two encryption schemes and the two decryption schemes of the encryption algorithm are slightly different. When the security of the encrypted image is desired to be lower, the encryption and decryption operations of the image are desired to be faster, the quality of the decrypted image is desired to be higher, the first encryption scheme should be chosen. When the security of the encrypted image is desired to be higher, the encryption and decryption operations of the image are desired to be slower, the quality of the decrypted image is desired to be lower, the second encryption scheme should be chosen. Therefore, according to actual cases, the corresponding encryption and decryption of images should be studied and chosen to meet practical requirements.
