| 摘要 |
PURPOSE:To simplify the constitution of an adding device of Galois field by deciding the large (m) and small (l) values of exponents of original alpha<1> and alpha<j> of a Galois field GF(2<q>) and delivering an exponent expression signal of alpha<i>+alpha<j> from (l) and a signal 1+alpha<m-X> with which a signal m-l is obtained as an address signal. CONSTITUTION:Original signals alpha<i> and alpha<j> (inot equal to j) of a Galois field GF(2<q>) which are sent from input terminals 1 and 2 are supplied to ROM3 and 4 respectively. Then a size relation deciding circuit 5 decides the sizes of exponents (i) and (j), and signals of large and small exponents (m) and (l) and supplied to an addition circuit 12. This circuit 12 consists of an adder 15, a subtractor13 and an ROM14. A signal m-l obtained from signals (m) and (l) by the subtractor 13 is supplied to the ROM14 as an address signal. Then the read-out signal 1+alpha<m-X> and the signal (l) of the circuit 5 are added together by the adder 15, and an output signal of exponent expression for alpha<m>+alpha<X>=alpha<i>+alpha<j> is delivered. |
