| 摘要 |
<p>A method for generating a value for a modular multiplicative inverse of an element of a Galois Field GF(2n). A first (R0), a second (R1), a third (R2) and a fourth (R3) register are provided, wherein the first register stores n+1 bits, and wherein the second, third and fourth register store n bits. The third and fourth registers carry out, by a single left shift, a division operation by x modulo the generating polynomial (g(x)) of the Galois Field. The generating polynomial (g(x)) of the Galois Field is stored in the first register. The field element to be inverted is stored in the second register. Zeros are stored in the third register. A 1 bit is storing in the left cell of the fourth register and zeros are stored in the rest of the cells of the fourth register. The contents of the second register (R1) is added to the contents of the first register (R0) while adding simultaneously the contents of the fourth register (R3) to the contents of the third register (R2), so as to convert the bit of value 1 in the left cell of the first register into 0. The contents of the first register (R0) is added to the contents of the second register (R1) while adding simultaneously the contents of the third register (R2) to the contents of the fourth register (R3), so as to convert the right-most bit of value 1 in the second register into 0. Shift-left operations are performed simultaneously on the first register and the third register and shift-left operations are performed simultaneously on the second register and the fourth register. By doing so, bits of value 1 stored in the second register are canceled by canceling bits both from the most significant location and from the least significant location of the second register.</p> |
