Integration of Data Compression and Cryptography: Another Way to Increase the Information Security

The main purpose of data compression is to reduce the memory space or transmission time, while that of cryptography is to keep the security of the data. So far, these two technologies have been studied separately. This is because any data can be compressed if necessary, and then encrypted. The problem is that, with the rapid progress in computing technology, the encrypted data will not be secure any more after a few years. Once the data are decrypted, all secret will be leaked. To solve this problem, in this paper we propose a new way to increase the information security through integration of data compression and cryptography. Specifically, the data to be considered here are images, and the compression technique is the k-PCA, which was proposed by us recently for image compression. The main advantage of using k-PCA is that this technique is data-dependent. Unlike other existing universal compression techniques, such as DCT, DWT, and so on, the non-linear transformation function used in k-PCA are found using the data to be compressed. Thus, even if the encrypted data are deciphered by some malicious persons, it is hard for them to reconstruct the images without the transformation function, which is encrypted and kept by the user as a secret key. To encrypt the compressed data and the transformation function, we can use any existing techniques, as long as they are relatively secure.