| 摘要 |
PURPOSE:To prevent the reduction in intensity of ciphering by splitting digital image data to be ciphered into rectangular regions, regarding image data included in each rectangular region as a matrix and using a product between the said matrix and the matrix formed by a cihering key as chphered data. CONSTITUTION:Data stored in an image memory 1 is split into mxn rectangular regions 2 virtually, and the data is ciphered at each region. Ciphered key data is stored in a key register 3 and used as the initial value of a pseudo random number series generator 4. An upper triangle matrix generation section 5 generates an upper triangle matrix D having the pseudo random number series as its component. On the other hand, a constant matrix storage memory 6 stores a predetermined regular constant matrix A. The result of multiplication between the upper triangle matrix D and the constant matrix A and an original picture data P13 are subjected to matrix multiplication and the result is outpulled as ciphered data of a rectangular region P14. Thus, no scramble signal is erased even when the difference or exclusive OR operation between two ciphered images is taken. |
