Efficient technique for image cryptography using Sudoku Keys

Abstract This Paper work proposes an Image cryptographic technique based on the Sudoku solution. The Sudoku solution can be reduced to a proper key clue by increasing the complexity level. The reduced clue for the Sudoku serves as the base key, which can be solved both at the Encryption and Decryption phase to reveal the Sudoku solution. Since a proper key clue leads to only one sudoku solution, the key is always stable. The Sudoku solution is expanded to the size of the Image to be encrypted using a sequence of expansion techniques. These techniques involve Number filling of the key matrix, Linear X-Y rotational shifting and Standard Zig zag pattern based reverse shifting. The derived cryptokey for an image dictates the details of positions to which the image pixels have to be shuffled. The shuffling is made at two levels namely Pixel level and Sub-Pixel (RGB) levels for an image, with the latter having more effective encryption. As this image encryption involves position shuffling in RGB layers, this technique falls under the Image scrambling method with partial diffusion. The Source and Encrypted images are analyzed for the crypto quality and thereby derive out the Performance metrics. The Distribution level of the source image pixels in the encrypted image is visually assessed by the absolute difference image. The Performance metrics reveal that the cryptography is more efficient, when the Sudoku is treated as a square matrix cryptokey and effectively used.