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Multiply elements of Galois field

`c = gfmul(a,b,p) `

c = gfmul(a,b,field)

**Note**

This function performs computations in GF(p^{m})
where p is prime. To work in GF(2^{m}), apply
the `.*`

operator to Galois arrays. For details,
see Example: Multiplication.

The `gfmul`

function multiplies elements of
a Galois field. (To multiply polynomials over a Galois field, use `gfconv`

instead.)

`c = gfmul(a,b,p) `

multiplies `a`

and `b`

in
GF(`p`

). Each entry of `a`

and `b`

is
between 0 and `p`

-1. `p`

is a prime
number. If `a`

and `b`

are matrices
of the same size, the function treats each element independently.

`c = gfmul(a,b,field) `

multiplies `a`

and `b`

in
GF(p^{m}), where p is a prime number and m
is a positive integer. `a`

and `b`

represent
elements of GF(p^{m}) in exponential format
relative to some primitive element of GF(p^{m}). `field`

is
the matrix listing all elements of GF(p^{m}),
arranged relative to the same primitive element. `c`

is
the exponential format of the product, relative to the same primitive
element. See Representing Elements of Galois Fields for an explanation
of these formats. If `a`

and `b`

are
matrices of the same size, the function treats each element independently.

Arithmetic in Galois Fields contains examples. Also, the code below shows that

$${A}^{2}\cdot {A}^{4}={A}^{6}$$

where *A* is a root of the primitive polynomial
2 + 2x + x^{2} for
GF(9).

p = 3; m = 2; prim_poly = [2 2 1]; field = gftuple([-1:p^m-2]',prim_poly,p); a = gfmul(2,4,field)

The output is

a = 6