Public Key Cryptosystem for Graphics and Image Based on Integrating Random Scrambling Permutation and Ring Theory

Graphics and image are often of huge amount of data and with much redundancy．For taking into account of these characteristics and for the efficient implementation of the digital image encryption/decryption and making use of the advantages of public key features,a three-dimension random matrix scrambling permutation and a Gray scrambling permutation are proposed,which creates a large cipher key space of at least N⁶ keys for N-ordered image．Combining with the improved version of NTRU,a new public cryptosystem for digital graphics and image is proposed．Analysis shows that this cryptosystem is of low time complexity and can protest against chosen plaintext attacks．The experiments with our implementation of the cryptosystem for digital multimedia show that many multimedia format such as digital image of BMP,PNG,or PCX format,digital audio of wav or au format,and TXT or DAT format text can be quickly encrypted using public keys and decrypted using private keys．