| 摘要 |
The controller (1) includes a central processing unit (2), a RAM type work memory (4), a program memory (3), and a computational cell (5). The program memory stores a subroutine for enciphering or deciphering digital message words by computing an exponentiation modulo N of each of the digital message words, N being an integer of high predetermined value. The exponentiation modulo N of a digital message word is computed by performing a sequence of operations A.B modulo N, where A and B are computational variables which depend on the value of the digital message word. Each of the operations A.B modulo N is performed by the central processing unit in cooperation with the computational cell. The cell has access to the RAM memory. On behalf of the central processing unit it executes computations of the type T + y.N where T and y are computational variables having integer values. Such a controller can be constructed in the form of a single small-sized chip. <IMAGE> |
